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Edited by ALEXANDER FINDLAY, D.Sc. 


THE MOLECULAR VOLUMES OF 
LIQUID CHEMICAL COMPOUNDS 

FROM THE POINT OF VIEW OF KOPP. 


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THE 


MOLECULAR VOLUMES 
OF LIQUID 

CHEMICAL COMPOUNDS 

FROM THE POINT OF VIEW OF KOPP. 


BY 

GERVAISE LE BAS, B.Sc. (Lond.) 

M 


WITH DIAGRAMS 


LONGMANS, GREEN AND CO. 

39 PATERNOSTER ROW, LONDON 

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BOMBAY, CALCUTTA, AND MADRAS 
1915 

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PREFACE. 


The work which has been attempted in the present 
volume is an application of the theory of molecular volumes 
from the point of view of Kopp, to a study of the 
constitutions of organic compounds chiefly. The working 
out of the theory thus reverts to the line of its historic 
development, the interval, representing a period of twenty- 
five years, marking no advance at all along this line. 
One reason is, that when the last important work was 
done, the question of the possible influence of constitutive 
influences on a physical property was not so prominent as 
it is to-day. The writers were, for the most part, content 
to point out that Kopp’s additive rule suffered limitations, 
without inquiring into the reasons for this, and giving to 
the deviations their proper interpretation. We might, 
perhaps, except the work of Thorpe, which is thoroughly 
imbued with the modern spirit. It is, however, just these 
limitations of the additive rule which are so useful to the 
chemist in his endeavour to work out the details of the 
structure of chemical compounds. This has been turned 
to good account in most of the physical properties, and the 
success which has attended the work in these directions, 
has probably contributed to the comparative neglect of 
molecular volumes. Another reason is that, so long as 
Kopp’s original values for carbon and hydrogen were 
retained, it was impossible to put the subject on a satis¬ 
factory basis, because, under the conditions, the evidence 
for one of the most important constitutive effects—that of 
ring structure—was completely obliterated. The following 
features of the old theory are retained: (a) Kopp’s con* 

V 

331002 


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VI 


PREFACE. 


ception of molecular and atomic volumes, and (b) the 
recognition of the additive principle. We are also 
indebted to those careful and patient workers, through 
whose laborious experimental researches that large amount 
of data which at present exists has accumulated. This has 
resulted in the detection of certain volume disturbances in 
the case of particular compounds the meaning of which 
was not at the time fully realized. These have of course 
been considered, and given what we believe to be their 
proper interpretation. Nearly all the atomic volumes 
have been modified; some are strikingly different from 
the old numbers. We also find it necessary to consider 
a larger number of atomic values for say, oxygen or 
nitrogen, than on the old theory. The result of these 
changes in the atomic values is a corresponding change in 
the conclusions drawn from the data. Whilst abundant 
material then existed for a fairly extended theory, it was 
found impossible to deal adequately with the subject, 
chiefly because of the initial errors in the values of the 
fundamental atoms, as well as on account of the im¬ 
perfect conceptions of chemical constitution which then 
existed. We cannot claim to have elaborated a perfectly 
satisfactory system, but the initial mistakes have been 
corrected, and we believe that the work is progressing 
on the right lines. At least there has been an honest 
endeavour to correctly interpret facts, and we have not 
knowingly subjected the evidence to an undue strain. 

The difficulties which one is likely to meet with in 
a research like the present one are great, for, owing to an 
embarras des richesses , one cannot at once distinctly perceive 
the relative importance of the facts which emerge, nor 
clearly distinguish real from imaginary regularities. Facts 
are liable to interpretation in so many ways. The want 
of an unifying principle has been keenly felt, but we 
believe that certain of the explanations which one feels 
instinctively to be slightly unsatisfactory, and which do not 
seem to fit in well with other explanations, are really 


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PkEFACE. 


vii 

different aspects of one and the same thing. There are 
doubtless fundamental features which have not yet been 
grasped, and which might serve to link up facts at 
present somewhat disconnected. 

Although we may have to wait for a thorough and 
scientifically worked out theory, we desire to lay stress on 
the good results which have already been obtained. The 
chief of these is undoubtedly the influence of ring structure 
and the evidence therefor. No physical property is ap¬ 
parently so well adapted to elucidate the ring structure of 
a compound as molecular volumes, and it is to be hoped that 
this will henceforward take its legitimate place among 
other physical properties as an instrument of research. 

A study of molecular volumes, especially, has shown 
us that probably we are not at the end of the utility of 
physical properties as means for giving us an insight into 
the structure of molecules. When a more scientific 
method of examination of these physical properties shall 
have been worked out, there is no doubt that a great 
advance will be made in a knowledge of the intricacies of 
chemical constitution. It is doubtful if the possibilities in 
this direction are as yet generally realized. 

Closely connected with the above subject, are a number 
of very important theoretical questions, such as the intimate 
structure of liquids, the nature of the atom and molecule, 
etc., but we have carefully avoided introducing these 
speculative questions into a more or less systematic work 
like the present 

We might, perhaps, note in passing, that the theory of 
molecular volumes, which is based upon an alternative 
conception of the structure of liquids, viz.: that due to 
Traube, has not been so successful as anticipated. An 
examination of current work shows how pessimistic is the 
spirit which obtains with reference to it Thus we find in 
a recent textbook* on physical chemistry, “Beyond the 

* The Relations between Chemical Constitution and some Physical 
Properties , by Dr. Smiles, chap, iv., pp. 145-6. 


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PREFACE. 


viii 

detection of association, volume relations are of little use 
in solving questions of constitution,” and again, . 

The prospect of such a method is not very bright . . . . ” 
Leaving aside the fact that Traube’s theory is based upon 
a number of assumptions which are doubtful, we should 
note that it does not answer to the test of all theory, viz. 
utility as an instrument of research, and an accumulation 
of good results obtained. A theory, like a tree, should be 
estimated by the quantity and quality of its fruit. Hitherto 
the crop has not been extensive. 

The data have been chiefly obtained from Clarke’s 
Constants of Nature , Part I., the Chemiker-Kalender ; and 
from many of the original papers to be found in the 
English and German scientific journals. 

We desire to express our gratitude to Prof. W. J. Pope, 
F.R.S., for the kindly help and encouragement extended 
for a period of eight years or so, during which most of the 
matter included in the present volume has been in course 
of preparation. 

G- Le B. 

15 October , 1915. 


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CONTENTS. 


CHAPTER PAGE 

I. The Molecular Volumes of Organic Compounds at the 

Melting-Point .i 

The hydrocarbons : paraffins, olefins, and acetylenes. The 
atomic volumes of carbon and hydrogen, i. The 
influence of the alternating factor, 4. The effect of 
unsaturation at the melting-point, 6. The nitriles, 

7. Oxygen compounds : the alcohols, ketones, and 
fatty acids. The volume of hydroxylic oxygen, 8. 

The volume of ketonic oxygen, 9. The volume of 
carboxylic oxygen, 11. Ring compounds, 14. 

II. The Molecular Volumes of the Hydrocarbons at the 

Boiling-Point.17 

The open-chain compounds: paraffins, olefins, and di¬ 
olefins, 16. The volumes of carbon and oxygen, 17. 

The influence of the homologous increment CH 2 , 22. 

The branching of the hydrocarbon chain, 25I The 
interaction between the iso group and ethenoid 
linkage, 26. Closed-chain hydrocarbons—simple and 
compound rings, condensed and separated rings, 33. 

The effect of self-affinity on the side-chains of 
aromatic compounds, 35. The polymethylenes, 46. 

The naphthenes, 51. A general study of the 
terpenes: hemi-terpenes, olefin terpenes, menthan 
terpenes, camphan terpenes, sesqui-terpenes, and di- 
terpenes, 53. The effect of cross-linking and bridging 
of the ring on the magnitude of the contraction, 67. 
Connexion with unsaturation, 68. Ring systems, 71. 
ix 


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X 


CONTENTS. 


PAGE 

III. The Molecular Volumes of the Halogen Compounds. 74 

Fluorine, 74. Chlorine, 76. Bromine, 79. Iodine, 81. 

The branching of the hydrocarbon chain, 83. Partial 
rings, a, ft and y halogen compounds, 85. The in¬ 
fluence of the ethenoid linkage, 88. Application of 
principles to complex compounds, 92. Aromatic 
halogen compounds, 93. The gradual chlorination of 
benzene, 94. 

IV. The Molecular Volumes of Organic Compounds contain¬ 

ing Oxygen.97 

The volume of oxygen in the alcohols, 98. The branched- 
chain compounds, 99. The volumes of ft and y 
di-hydroxy compounds, 100. The phenols, 104. Ter- 
penic or ring alcohols, 106. The ethers, 108. The 
position and nature of liquid water, 109. The effect of 
the addition of the homologous increment CH 2 on the 
volumes of the ethers, 113. The symmetrical and un- 
symmetrical ethers, 116. Formula representing results 
for complexity and symmetry in the ethers, 119. An 
examination of the various constitutive effects associ¬ 
ated with hydrocarbon chains, 120. Complexity, 120. 
Compactness of molecules, 121. Heterogeneity, 123. 
Symmetry, 126. The phenolic and other ethers, 127. 

The o, m, and p cresylic ethers, 130. Oxygen with 
double linking, 133. The aldehydes and ketones, 134. 

The carboxylic acids, 140. The fatty esters, 142. The 
effect of the homologous increment on the ester series, 

144. The methyl, ethyl, and propyl salts of the fatty 
acids, 147. Causes of variation in volumes of isomers 
and of the influence of symmetry, 150. Unsaturated 
oxygen compounds, 153. The substituted esters, 

155. The volume of oxygen (: 0 ) in union with sul¬ 
phur, nitrogen, and phosphorus, 161. The aromatic 
acids and esters, 163. The volume of ring oxygen, 

168. A summary of the mode of variation of the 
oxygen atoms in organic compounds, 173. 

V. The Molecular Volumes of Sulphur Compounds . .178 

The volume of the element sulphur, 178. The halogen 
derivatives of sulphur with and without sulphur, 180. 


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CONTENTS. 


xx 


PAGE 

A study of the constitutions of certain sulphur com¬ 
pounds investigated by Thorpe, 182. The sulphur 
oxides, acids, and esters, 184. Doubly bound sulphur, 

186. Ring compounds including sulphur, 187. The 
thio-alcohols (mercaptans) and ethers, 188. Selenium 
and compounds, 189. Chromium compounds, 190. 

VI. The Molecular Volumes of Nitrogen Compounds . 191 

The element nitrogen and NClj, 192. The nitriles and car- 
bylamines, 193. Cyanic acid and the esters, 193. 
Nitrogen compounds containing sulphur, 195. The 
amines, 197. The diamines and derivatives including 
ring compounds, 203. Aromatic amino compounds, 

208. The oxides and esters of the nitrogen acids in¬ 
cluding the corresponding aromatic compounds, 213. 
Alkaloid derivatives containing nitrogen, 222. 

VII. The Molecular Volumes of Phosphorus Compounds, etc. 223 

The element phosphorus and phosphorus oxides, 223. 
Phosphorus compounds containing oxygen, halogens, 
and sulphur, 227. Trivalent and pentavalent nitrogen, 

229. Compounds of arsenic and antimony, 232. 

Elements of Group 4: Silicon, titanium, vanadium, ger¬ 
manium, 233. 

Miscellaneous elements: Boron, zinc, 234. 

VIII. Summary of the Theory of Molecular Volumes . . 235 

A. The Additive principle with Table of atomic volumes, 

235. Variations in the volumes of the atoms, 237. 

B. Constitutive influences: (a) The influence of the homo¬ 

logous increment, 239. ( 6 ) The influence of unsatura¬ 
tion, 241. (c) Partial ring structure, 245. (d) Ring 

structure, 246. (e) Molecular volume and valency, 

247. (/) The constitutive influences due to special 

groups, 249. 

C. A discussion of the special conception embodied in 

molecular volumes, and the relation which obtains be¬ 
tween this property and other physical properties such 
as boiling-point, surface tension, viscosity, etc., 249. 


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i CONTENTS . 

PAGE 

IX. Appendices:— 

i. A Formula by means of which the molecular volume at 


the boiling point may be calculated . . . .263 

11. An Investigation of the Dicarboxylic Esters . . . 265 

Table of References .273 

Bibliography .275 


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CHAPTER I. 


THE VOLUMES OF ORGANIC COMPOUNDS AT THE MELTING- 

POINT. 

Open Chain Compounds. 

The hydrocarbons: n paraffins, olefins, and acetylenes. 

The atomic volumes of carbon and hydrogen. 

The highly constitutive nature of the melting-point probably 
makes it generally unsuitable as a condition of comparison of 
the molecular volumes of compounds. Nevertheless, in certain 
cases, where the effect of constitution is constant, some remark¬ 
able regularities have been observed, and since the results in 
general agree with those under other conditions, we may con¬ 
sider them to be significant. 

In 1907 the author 1 dealt with a long series of normal 
paraffins C n H 2 „ +2 , and showed that the volumes of the compounds 
in the liquid state, at the melting point, form an approximately 
arithmetical series, similar to that of their valencies. Thus if 
V m represent the molecular volume of a member of the series 
C*H 2n+2 , under the conditions, and W the sum of the valencies, 
—C = 4, H= I—then the ratio V^/W is constant, and equal to 
2*970 approximately. This is one-sixth of the difference for 
CH 2 , viz. 17*82. 

The data are those of Krafft, 2 who also showed that the 
difference for CH 2 is constant, and equal to 17*80. 


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2 


LIQUID CHEMICAL COMPOUNDS, 


TABLE I. —Thb Volumes of the Normal Paraffins. 


Hydrocarbons . 

W. 

M. Vol. 

= v m . 

A for CH a . 

V w /W = S. 

W x 2*970 
= M. Vol. 

Undecane . . C 11 H S4 

Dodecane . . C 19 H % 

Iridecane . . 

Tetradecane . . C 14 HjQ 

Pentadecane . . C 15 H 89 

Hexadecane . . C K B M 

Heptadecane . . C 17 H 36 

Octadecane . . 

Nonadecane . . € 3S H tfi§ 

Eicosane . . C^H 48 

Heneicosane . . C S1 H 44 

Docosane . . Gjtl m 

Tricosane . . 

Tetracosane . . C 24 H M 

Heptacosane . . 

Hentriacontane . CgjH^ 

Dotriacontane . 

Pentriacontane . CggH 7a 

Mean Values 

68 

74 

80 

86 

92 

98 

104 

no 

116 

122 

128 

134 

140 

146 

164 

188 

194 

212 

201*4 

219*9 

237*3 

255*4 

273-2 

291*2 

3090 

326*9 

344*7 

362*5 

380*3 

398-3 

416-2 

4341 

487-4 

558-4 

5762 

629-5 

• •{ 

18*5 

17*4 

18*1 

17*8 

18*0 

17*9 

17*9 

17-8 

17-8 

17-8 

18*0 

17*9 

17*9 

3 x 17*8 

4 x 1775 

17*8 

3 X 17-8 

17-83 

= 6 x 2*971 

2*962 

2*971 

2*966 

2-970 

2*970 

2 - 97 1 

2*971 

2*972 

2*971 

2*971 

2*971 

2*972 

2*971 

2*973 

2*972 

2*970 

2*970 

2*969 

2*970 

20196 

219*78 

237*6 

255*42 

273*24 

291*06 

308*88 

32670 

344*52 

362-34 

380* 16 

398-oo 

415-8 

433-62 

487*08 

558-36 

576-18 

629*64 


The above simple relation may be interpreted as follows:— 
(a) The volumes of the atoms, carbon and hydrogen are 
respectively the same in the individual compounds, but if only a 
slight change occurs from compound to compound, these volumes 
may be demonstrated by a comparison of a series of volumes. 

( [b ) The volumes of carbon and hydrogen are 
[H] = 2 970 and [C] = 4 x 2 970 = 1188, 
and the relation (1:4) between these, is similar to that existing 
between the valencies of carbon and hydrogen. The above 
numbers are of course only average ones, but there is evidence 
of only very small apparent deviations therefrom. 

Also [CHJ = ii*88 + 5*94 = 17*82. 


Direct Calculation of the Atomic Volumes of Carbon and 
Hydrogen . 

2[H] = [C^H*,] + [C 16 H3J - [C S1 H W ] 

= 273*2 + 291*2 - 558*4 = 6*o 
2[H] = [CjgHjJ - 18 [CHJ = 326*9 - 18 x 17*83 = 5*96. 

The volume of hydrogen is thus very nearly equal to 3 0. 

Also [C] = [CHJ - 2[H] = 17*83 - 6*0 * 11*83. 


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ORGANIC COMPOUNDS AT THE MELTING-POINT. 


3 


The relation between these values is 

J§5 = = 4*0 (approx.). 

[H] 30 

These data give us the means of calculating the volumes of 
the hydrocarbon elements in compounds at the melting-point. 

[C„H 2n + J = »[C] + (2» + 2)[H] 

= (6 n + 2)[H] = (6 n + 2) x 2*970. 

Such values are found in the last column of the previous 
table. 

Krafft studied the molecular volumes of the above paraffins, 
not only at the melting-points, but also at a number of tempera¬ 
tures up to ioo°C. This enables us to compare the volumes of 
the paraffins at any temperature within these limits by making 
use of interpolation formulae 3 of the type— 

di = ff-r 1 ! - at ± fit 2 }, where t = T - T 1 . 

The results are recorded in the following table:— 

TABLE II. —Values of Vm/W illustrating the Additive Rule. 


M.P.+ n x 10 

CijHjh 

CA 

^14^80 

^16^32 

^16^34 

CnH* 

^18^38 

M.P. 

. 

2*971 

2'966 

2-970 

2*970 

2*971 

2*971 

2-972 

tt 

+ IO° 

2*997 

2*993 

2*994 

2*997 

3*000 

2-998 

2*999 

tt 

+ 20° 

3025 

3*020 

3*023 

3-024 

3*027 

3*025 

3*026 

tt 

+ 30° 

3*053 

3*049 

3*051 

3*052 

3*054 

3*053 

3*053 

tt 

+ 40° 

3-081 

3*078 

3*081 

3*080 

3*082 

3*081 

3*082 

tt 

+ 50° 

3*iii 

3-107 

3*109 

3-iog 

3* 111 

3*iio 

3* io 9 

tt 

+ 6o° 

3*i4i 

3*137 

3*139 

3*140 

3*140 

3*138 

3*137 

tt 

+ 7°° 

3172 

3*i68 

3*170 

3*169 

3-170 

3-166 

3*166 

tt 

+ 8o° 

3-206 

3200 

3-201 

3*200 

3201 

— 

— 

a 

+ 90° 

3*240 

3*232 

3*234 

— 

— 

~ 

~ 


The above table shows that, at equal intervals of temperature 
from the melting-points, and in the liquid state, the volumes of 
the compounds are related to each other in a similar way to that 
at the melting-points. 

The effect of homology, or the effect of want of strict simi¬ 
larity between the volumes of the atoms in the different terms of 
the series, is here at a minimum, and is in contrast to what we 
find under other conditions, such as the boiling-point. The 
nearly accurate manifestation of the additive rule extends to the 
neighbourhood of ioo°, but under the latter condition there are 
signs of a slight relative expansion among the more complex 
members of the series. 

1 * 


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4 


LIQUID CHEMICAL COMPOUNDS. 


i. The Influence of the Alternating Factor. 

If the differences for CH 2 , as also the values V w /W, be ex¬ 
amined (see Table I), it will be found that they alternate in a 
remarkable way among the earlier members of the series. This 
is also found to be true of the melting-points, as was first pointed 
out by Baeyer 4 in the case of the fatty acids and other series. 
This is, however, a feature hitherto unrecognized in molecular 
volumes, and it is evident that the peculiarity which causes the 
melting-points of successive terms to alternate, also similarly 
affects the molecular volumes. The data for compounds 
simpler than undecane have been calculated by extrapolation 
from Krafft’s data (loc. cit.), with the result that the effect has 
been traced to simpler compounds, where it is more marked. 
The melting-points of nonane C 9 H 20 and decane C 10 H 22 are 
- 51 0 C. and - 2 5 0 C. respectively. 


TABLE III.— The Effect of the Alternating Factor on the Molecular 
Volumes of the Liquid Normal Hydrocarbons . 5 




Vm 


A between 

A between 



Substance. 

W. 

at 

A. 

Odd 

Even 

V w /W. 

£ 

Tf 

> 



m.p. 


Members. 

Members. 

C.H* 

56 

165*67 

18*9 



2*957 

— 

^10 H 22 

62 

184*54 

169 

35*7 


— 

2*976 

ChHjh 

68 

201*40 

18*5 


35*4 

2*962 

— 

CuHjj 

74 

219*90 

17*4 

35*9 


— 

2*972 

Cia^aa 

80 

237*30 

18*1 


35*5 

2*966 

— 

C14H30 

C 15 H32 

86 

255*40 

17*8 

35*9 

35*8 

— 

2*970 

92 

273*20 

18*0 

) 

2*970 



^16^84 

98 

291*20 

17*8 

35*8 


— 

2*971 

104 

309*00 




2*971 



It is apparent from the above table, that a difference in 
volume exists between the odd and even members of the hydro¬ 
carbon series below hexadecane C 18 H 84 . 

The odd members of the series have relatively small volumes, 
but this depression gradually disappears as we ascend the series, 


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ORGANIC COMPOUNDS AT THE MELTING-POINT 5 

for in the table, the values of V w /W gradually increase to a 
constant value—2*971. 

The even members of the series have relatively large volumes, 
and this abnormal expansion gradually diminishes as the series 
is ascended until at about hexadecane C 16 H 34 the value of V w /W 
is constant, or nearly so. 

It follows that the values of V w /W, which respectively refer 
to the odd and even terms of the series, can be arranged along 
two curves, which respectively represent values which are either 
depressed below, or raised above those which would belong to a 
mean curve, or one for which V m /W is consistently 2*971. The 
two curves are practically coincident with each other, and with 
the mean condition, after C 16 H 34 . The alternating factor thus 
exerts an opposite effect on an odd or even member, of the series, 
these respectively possessing an odd and even number of carbon 
atoms in the chain. 

The influence of the alternating factor upon the volume fol¬ 
lows as a direct consequence of its effect upon the melting-point. 
We have no reason to suppose that this alternating factor, which 
may be considered to be due to a specific property of the mole¬ 
cules, specially affects the liquid volumes, but is only rendered 
evident by differences between the melting-points. Since the 
volumes are a function of temperature, they would naturally also 
be affected. The result is, that the melting-points of the odd 
numbers of the series are depressed and the volumes diminished 
below a mean condition, whilst the melting-points of the even 
members are elevated, and the volumes augmented above this 
mean condition. The phenomenon just noted is doubtless 
connected with the question of residual affinity. The members 
of the even series evidently require a higher temperature for the 
odd series in order to cause those changes which make possible 
a relative motion of the molecules. Beyond this we know very 
little. Biach 6 has endeavoured to account for the alternating 
effects apparent in the melting-points of other series by means of 
residual affinity. If we suppose that every pair of CH 2 groups 
in the chains partially compensate each other, we see that there 
would be an excess of residual affinity when the number is odd, 
and a defect when even. This would cause a relative rise in 
boiling point and diminution in volume in the case of the first, 
and vice versd. 


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j6 


LIQUID CHEMICAL COMPOUNDS. 


The Effect of Unsaturation on the Molecular Volume at 
the Melting-Point . 7 

The detection of such a constitutive feature as the influence 
of the alternating factor, suggests the possibility of unsaturation 
under similar conditions, influencing molecular volumes. For¬ 
tunately the data are at hand to put this question to the test. 
These refer to the olefins C n H 2 J = | and the acetylenes C„H 2n _ 2 |=|, 
and are due to Krafft. 8 It will be convenient to draw our 
conclusions simply from the differences, because the value of CH 2 
is the same in the unsaturated series as in the normal paraffins. 
This shows that the saturated atoms possess similar volumes in 
saturated and unsaturated compounds, and that thus the effect 
of unsaturation is only local. 


TABLE IV.— The Value of the Effect for Unsaturation. 


Substance. 

V w at 

A. 

Substance. 

Vm at 

A. 


m.p. 



m.p. 


Dodecane C lS H M 

2199 

87 

Hexadecane CjgH^ 

291*4 

8-5 

Dodecylene | = ] 

211*2 

Hexadecylene C lft H M | = | 

282*9 



6*2 



6*8 

Dodecylidene |=| 

205-0 


H exadecylidene CjgHgo |= | 

2761 


Tetradecane C^Hg,, 

2 55‘4 

8-5 

Octadecane C 18 Hgg 

326*9 

8-3 

Tetradecylene C 14 H S8 [ = ] 

2469 

Octadecylene | = ] 

3186 

6-8 

6-4 

Tetradecylidene C 14 H 26 1=] 

240-5 

Octadecylidene J=J 

311*8 

1 



It is apparent that unsaturation exerts a special effect on the 
molecular volumes under the above conditions. This is doubt¬ 
less to be expected, since the molecules at the melting-point 
acquire characters of fixity which precludes relative motion, and 
because the molecular centres are less than at, say, the boiling- 
point. 

If we compare the volumes of the corresponding members of 
any two series, we shall find that the differences are the same 
throughout, and that those which exist between any two of the 
terms in the three series are respectively some multiple of 17*8. 
These facts indicate (a) that the effect of single and double un¬ 
saturation is constant, and ( b ) that the atomic volumes of carbon 
and hydrogen are the same in the three series. 

The effects due to unsaturation are calculated thus:— 


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ORGANIC COMPOUNDS AT THE MELTING-POINT. 


7 


-2[H] + M 

= [C n H* n | = |- CnH^+J = - 8-5 

But 2[H] = 2 x 2*97o = 5*94. 

Therefore | = ] = - 8*5 + 5*94 = - 2*56. 

Also - 4 [H] + [=] 

= [C«H an _ J [=| — C n H an + 2 ] — = 15*1 
But 4[H] = ii*9 

.*. |=| = - 15*1 + n-9 = - 3*2. 

The depression caused by an olefin linkage | = | is equal to 
- 2*56, and that for an acetylene linkage |=| is - 3 2. 

These results show that a special effect due to unsaturation is 
observable at the melting-point, and this is in agreement with 
the conclusions drawn from the observation of other physical 
properties. One difference, however, is that, whereas, in optical 
refractivity and magnetic rotatory power, an increase in the 
magnitudes of the constants is observable, in molecular volumes 
on the other hand a decrease is noticed. These differences are 
what we should expect. It is to be supposed that the nearer 
that absolute zero is approached, constitutive effects like these 
become more marked. There is also the possibility that at the 
boiling-point, when the distance between the molecular centres is 
greater than at the melting-point, the effect for unsaturation may 
disappear altogether. The melting point is a highly constitutive 
property, and these temperatures are not related to each other 
in the same way as the boiling points of compounds. For this 
reason, the volumes referred to the melting-point, are not as a 
rule comparable with those referred to the boiling-point. The 
constitutive factors vary least from compound to compound, 
among the normal paraffins. 

The Nitriles. 

In addition to the hydrocarbons, and particularly the un¬ 
saturated ones, Kraflft 9 has also studied the alkyl cyanides or 
nitriles at the melting-point. They are unsaturated in a similar 
sense to the acetylenes, as a comparison of their formulae will 
show; 

R - C = CH R - C = N 

Acetylenes. Nitriles. 

The volume of combined nitrogen is— 

[=N] = 3 [H]. 


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8 


LIQUID CHEMICAL COMPOUNDS, 


On this assumption, we shall see from the following table, 
that there is an outstanding difference for unsaturation, on com¬ 
paring the observed and the calculated values. 


TABLE V. —The Volumes op the Nitriles. 
R - C = N. 


Substance. 

W(R). 

V m . 

A for CH a 

Vol. R. 

- C = N. 

Lauronitrile C 11 H as C = N 

67 

216*8 


199*0 

17-8 

Myristonitrile C = N 

79 

252*3 

35*5 

2346 

17*7 

Palmitonitrile C 16 H S1 C = N 

9 i 

288*2 

35’9 

270*3 

17-9 

Stearonitrile C = N 

103 

324*0 

35-8 

305 9 

18-1 

Mean Values . 

• 

u 

35’7 
x 17-85 


17-87 


The group - C = N evidently equals that of CH 2 in volume. 

On the assumption that 

[C] = 4 [H]and[N]==3[H] 

- C EE N = 7[H] = 20*8 (calc.) 

A for |=[ = 17*87 - 20*8 — - 2*93. 

Oxygen Compounds: Ketones and Fatty Acids. 

(Krafift, loc. cit.) 

Hydroxylic Oxygen (OH). 

The melting-point is a physical property very sensitive to 
constitutive influences, and it is necessary to obtain the substance 
quite pure in order to show a melting sharply at one temperature. 
Slight traces of impurity are a serious impediment to an accurate 
determination. Some impurities are particularly difficult to get 
rid of, such as small quantities of substances belonging to the 
same series as that of the compound which is being examined. 
It follows that an accurate study of molecular volumes is de¬ 
pendent on an accurate estimation of the melting-points of the 
substances. How far the discrepancies, observed in a study of 
the molecular volumes, are due to such inaccuracies, it is difficult 
to say, but some may be due, at least in part, to this cause. 

In drawing up a table of the alcohols we assume, what is very 
probable, that in each compound the atom of hydroxylic oxygen 
is equal in volume to twice that for a single hydrogen atom in 
the same compound, i.e. 

[O'] = 2[H]. 


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ORGANIC COMPOUNDS AT THE MELTING-POINT 


9 


TABLE VI.— The Normal Alcohols. 
Le Bas (loc. cit.). 


Compound. 

w. 

v*. 

Vm/W. 

W x S 

S a=S 2*970. 

Nonyl Carbinol 

c 10 h 21 oh 

64 

188*3 

2*943 

190*08 

Undecyl „ 

CjjHjjOH 

76 

223-9 

2-946 

225*72 

Tridecyl ,, 

C^H^OH 

88 

259-8 

2-953 

26l*36 

Pentadecyl „ 

Cj.HjjOH 

100 

296*0 

2*960 

297*00 

Heptadecyl „ 

c 18 h„oh 

112 

332*3 

2*970 

332 - 64 


An examination of the numbers shows that it is only at 
about heptadecyl carbinol that the value of V^/W approximates 
to the normal value of 2 970. 

There is a variation in the volumes as we ascend the 
series, which variation may be considered to be similar to those 
which we find at the boiling-point and due to the addition of 
the homologous increment CH 2 . The significance of this prob¬ 
ably is that, for the particular series in question, the compounds 
are not quite comparable at the melting-point. This want of 
correspondence between the two series—the melting-points and 
the molecular volumes—involves a difference between the volumes 
of the carbon and hydrogen atoms in the compounds from 
their usual values, derived from the normal paraffin series. 
The temperatures at which the volumes of these atoms are 
normal, are evidently not the melting-points. The value of 
hydrogen which has been noted, viz. : 2 970, is, however, likely 
to occur at the melting-point at some point of the series which 
is being examined. Among the alcohols, this occurs at hepta¬ 
decyl carbinol C 18 H 87 OH. 

Ketonic Oxygen (C : O). 

The melting-points of the compounds of this series show signs 
of alternation, and this fact may possibly influence the molecular 
volumes somewhat. 

The data, except for the more complex compounds, are of * 
miscellaneous origin. The latter are due to Krafft (loc. cit.). 

It is remarkable that, whilst the simpler compounds show 
values of V,»/W, which fall below the normal value 2 970, the 


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IO 


LIQUID CHEMICAL COMPOUNDS. 


most complex show values which are in excess of this. Com¬ 
pounds of the complexity of (C 6 H 13 ) 2 C : O, in their results, are 
similar to those of the paraffin series, in that the values of V m /W 
are = 2*970 exactly. 

[O"] = 3[H] = 3 x 2-970 = 8-91. 


TABLE VII. —The Volumes of the Ketones. 


w. 

Compound. 

m.p. 

v m . 

A. 

W x 2*970. 

A. 

63 

C 8 H„ . CO . CH, 

3*5 

186-2 

_ 

187-1 

+ 0-9 

69 

C 9 H 19 . CO . ch 8 

15-0 

204-4 

— 

204-9 

+ 0-5 

69 

C 6 H u . CO . C 6 H n 

14*6 

204-3 

— 

204-9 

+ o-6 

81 

CgHu • CO . C 6 H 13 

28-0 

240-6 


240-6 

_ 





35*6 



93 

C 7 H, s . CO . C,H, S 

40-0 

276*2 

2 x 17-8 

276-2 

— 





35-8 



105 

c 8 h 17 . CO . C 8 H 17 

49*o 

312-0 


311*8 

- 0*2 

141 

Laurone 

69-0 

420-6 

_ 

418-8 

-i-8 


^11^28 • CO . CnHjtf 






165 

Myristone . 



71*1 




C 19 H„.CO.C lS H„ 

76-3 

491-7 

4 x 17-8 

490*0 

-17 

189 

Palmitone . 



71-0 




CibH 81 . CO . C 15 H 31 

8a-8 

562-7 


56 i *3 

-i*4 


Stearone . 



71-6 



213 

CnHgj . CO . Cj.Hgg 

88-4 

634-3 


632-6 

-i*7 


Mean value 


• • -( 

71-2 






\ 

X 

» 

M 

II 

4 



It is probable, from the evidence of the above numbers, that 
the series of melting-points and the series of temperatures for 
which the volumes of similar atoms are equal, are not quite the 
same. We notice that the differences between the calculated 
and observed molecular volumes for laurone, etc., are the same, 
viz. I *70. 

The following results show that 

[O'T = 3[H] 

in the ketones, and that the apparent deviations therefrom, are 
due to disturbances of the total volumes of the compounds, for 
some reason similar to that already stated. 

Vm O" 

[C 16 H3oO] + 2[H] = 282-17 

897 

[CuHgJ = 273-2 

and [C^H^O] + 2[H] - 317-97 

8-97 

[CjtHjjJ = 309*0 


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ORGANIC COMPOUNDS AT THE MELTING-POINT. n 


This is sufficiently near to 8*91 = 3 x 2*970 = 3 H to make 
it probable that the volume of O' in the ketones is in reality equal 
to 3 H. 

Carboxylic Oxygen C : O (OH). 

The fatty acids C n H 2rt 0 2 are subject to the alternating factor, 
but sufficient data do not exist for a study of this subject in 
relation to them. 

Krafft, whose excellent experimental work has already been 
referred to, has extended his observations to a few mono- 
carboxylic fatty acids, which are connected with the compounds 
already studied. They correspond to those ketones which were 
shown to be normal in their atomic volumes. 


TABLE VIII.— Volumes of the Fatty Acids. 


Compound. 

W + 1. 

V m at m.p. 
(Krafft). 

A. 

V 

W + 1. 

Lauristic. 

Myristic . 

. C 12 H M O a 

77 

228*5 

35*9 

2*970 


89 

264-4 

35*8 

2*970 


Palmitic . 


IOI 

300*2 

2*972 

357 

Stearic . 


113 

335*9 

2*972 


Mean Value 

■ • ( 

35*8 





1 = 

2 x 17*9 



The above results indicate that amongst the carboxylic acids 
the relations [O"] = 3[H] and [O'] = 2H hold. 

Volume of C 0 2 . 

This may also be deduced in the way shown in the following 
table;— 


TABLE IX. 


Fatty Acid. 

v m . 

Paraffin. 

Vm. 

CO a . 

Lauristic 

• C^O, 

228*5 

C„H m 

201*4 

27*1 

Myristic . 


264*4 

CuH* 

237*3 

27*1 

Palmitic . 

• c 16 h w o 2 

300*2 

CbH* 

273*2 

27*0 

Stearic . 

• C w H le O, 

335*9 

c, 7 h* 

309*0 

26*9 



Mean Value 

. 

27*0 


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12 


LIQUID CHEMICAL COMPOUNDS. 


g[H] = 9 x 2*970 = 26*73. 

It follows that [C 0 2 ] = 9[H], and since [C] = 4[H], then 

2[0] = 5[H] =15 x 2*970 = 14*85. 

Volume of 0 2 . 

This is also shown to be the case by the following calcula¬ 
tions— 

Vm. O.. 

[Ci 4 H m OJ + 2[H] 270*37 

14*97 

[C^Hig] 255*4 

[CigH^OJ + 2[H] 306*17 

14*97 

[CieHjJ 291*2 

The value obtained by difference, is similar to the one calcu¬ 
lated. It is approximately equal to 5[H]. Remembering that 
[O"] = 3[H], in the ketones, and that [O'] =■ 2[H] in the alco¬ 
hols, we account for the value of O in the group - C^qjj 
as follows:— 

[O"] + [O'] = 3 [H] + 2[H] = 8*91 + 5-95 - 14*85. 

The carboxyl oxygen in the fatty acids thus possesses a similar 
volume to that of carbonyl oxygen in the ketones , and the remaining 
oxygen is hydroxylic as in the alcohols. 

The latter may be calculated independently as follows:— 

Vm. Vm. 

[CjjH^OJ (fatty acid) 228*5 

[CjsHaeO] (ketone) 2 4°’ 6 \ 2 22*8 

less [CHJ - 17*8J 222 * 

A for [O'] = 5*7(2 x 2*95). 

Whilst the results are what we may call normal for com¬ 
pounds of about the complexity indicated (C lc ), simpler com¬ 
pounds are evidently different. The reason has been indicated. 

Note on Pelargonic Acid. 

Besides those already noticed, we may remark that KrafIVs 
value for pelargonic acid (C 18 H 17 . COOH) of melting-point 12-5 
is 173*2, or — 

Vm = 173*2 observed. 2*Va 175*2. 

This is a number which is larger than the observed value by 
175*2 - 173*2 = 2*o, and consequently the latter is depressed to 
this extent below the normal. If, however, we compare the 
volume of pelargonic acid with a compound (alcohol) of similar 
complexity, we observe the following results :— 


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ORGANIC COMPOUNDS AT THE MELTING-POINT. 13 


Alcohol. 

Vm. Acid. 

V w . 

C, 0 H„O' 

188-3 C 9 H 18 0 ' 0 " 

173-2 


plus CH 2 

17-8 


2SnVa 

191*0 


Vm 

191*0 C 10 H„O" 

follows that 

[ 0 "] = 3 [H] since [O'] 

= 2[H]. Then 


[C 10 H 22 O"] - [C 10 H 22 O'] = [O"] - [O'] 

= 191*0 - 188*3 = 27 

which is a number but little different from the theoretical 
difference. 

CO"] - [ 0 ] - [H] - 2*97. 


Conclusion . 

We thus conclude that if at a certain point in a series 
the volumes of the carbon and hydrogen atoms are similar to 
their normal values, which have been deduced from a long list 
of normal paraffins from C 1€ H 34 to C 35 H 72 , the values for simpler 
compounds will fall short, and those for more complex compounds 
will be in excess of these. This indicates that there is probably 
a progressive increase in the atomic volumes of, say hydrogen, as 
measured by the ratio V m /W from quite the beginning of a series. 
This effect is, however, complicated by the alternating factor in 
alternating series. We shall observe what is possibly a similar 
result at the boiling-point, and it may be supposed to be due to a 
want of strict similarity between consecutive members of a series 
under these conditions. The mode of increase at the melting-point 
is, however, not quite so clear. In conclusion, we may note that 
it is probably true, that the molecular volumes of the various 
compounds in different homologous series, are not quite com¬ 
parable at the melting-point, and since the melting-points are 
not related to one another in the same way as the boiling-points 
of the same series of compounds, we must expect differences in 
the variations of the volumes of a homologous series at the two 
points respectively. 

As regards the atomic volumes in the carboxylic group, we 
have found that— 


[COOH] = [C] + [H] + [O'] + [O"] 

= ii*88 + 2-97 + 5-94 + 8-91 
= 29-7 (calculated) 

[COOH] = 30*0 approx, (by difference). 


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14 


LIQUID CHEMICAL COMPOUNDS. 


Note .—In order to show how the observed volumes may 
vary—for reasons unknown at present—Schiff, a very careful 
and accurate worker, found a value of 333 for stearic acid 
C^HggCOOH, whilst Krafft, on the other hand, found the volume 
to be 335*9 for this compound, and in view of the fact that the 
latter took special care to experiment with pure substances, we 
must give to his value at least equal weight to that which might 
be accorded to the other. Moreover, the larger number accords 
with those obtained for the neighbouring homologous fatty acids 
by Krafft This raises the question of why workers of equal 
reliability should obtain different experimental results, which 
differences, indeed, seem too large to be ascribed to the effect of 
impurity, but this can only be settled by very careful and accur¬ 
ate experimental work on substances prepared in several different 
ways. 

Ring Compounds. 

Schiff 10 determined the volumes of a number of aromatic 
compounds which are possessed of ring structure, in order to 
find out whether significant volume relations were to be met 
with, similar to those which Krafft had pointed out for paraffin 
derivatives at the melting-point. Schiff failed to find such re¬ 
lations, and indeed any significant relations whatsoever. 

The reason no doubt is, that the melting-point is a highly 
constitutive physical property, and if we are to consider the 
volumes of substances in the liquid state at the melting-point, 
we must expect large deviations from the values which might be 
expected from a consideration of their composition alone. 

If the compounds are in the liquid state at the melting-point, 
and we suppose that the structure of liquids does not change in 
the interval from the boiling to the melting-points, we must 
suppose that they are subject to the law of coincident states. 
Under such circumstances we might expect, that a condition of 
comparison would be found at equal fractions of the boiling- 
point. The melting-points are not equal fractions of the boiling- 
point temperatures of the compounds, and thus they do not 
represent a suitable condition of comparison, at least from the 
same point of view. 

The following investigation shows, that the volumes of com¬ 
pounds are comparable at approximately equal fractions of the 
boiling-point temperatures:— 


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ORGANIC COMPOUNDS AT THE MELTING-POINT . 15 


TABLE X. 


Compound. 

m.p. 

or 

0°. 

b.p. 

1 _ m *P* 

b.p. 
= A. 

d m.p* 

d b.p* 

dm.p. _ j 
db.p- 
= B. 

Ratio 

B/A. 

C.H. 

6° 

8o° 

0*210 

0*8940 

08133 

0*0980 

0*470 

c 4 h 4 s 

Cio H 8 

o° 

V 

0*236 

1*0884 

0-9874 

0*1023 

0434 

79 °-2 

217 0 

0*281 

0*9777 

0*8674 

0*1270 

0*456 

c 10 h i4 

o° 

200° 

0*423 

0*9419 

07809 

0*2062 

0*487 

C,4H 10 

. ioo°*5 

340 ° 

0*391 

1*0630 

0*9073 

0*1720 

0*440 

c 5 h 5 n 

o° 

II 5 ° 

0*296 

1*0033 

0*8826 

0*1367 

0*462 

CjH,N 

C„H«. C a H 4 

o° 

234 ° 

0*462 

1*1081 

0*9211 

0*2030 

0*439 

103° 

277 0 

0*316 

1*0300 

0*9018 

0*1422 

0*450 






Mean. . . 

0*455 


Conclusion .—This table shows, that at equal fractions of the 
boiling-points the molecular volumes of the compounds are 
similar although not exactly equal fractions of the volumes at 
the boiling-points. The nearly constant relation between A and 
B, indicates that there is a relation between the changes in 
volume of the molecules, and the changes in temperature, which, 
so long as the liquid state is maintained, is approximately the 
same for the ring compounds mentioned and others of similar 
type. The condition necessary for the volumes at the melting- 
points to show similar results relatively to each other, as at the 
boiling-points, is that A should be the same for all, or that the 
interval between the melting- and boiling-points should, in all 
cases, be the same fractions of the boiling-point. This condition 
is not realized, hence the volumes at the melting-points are 
subject to all the large and preponderant constitutive influences 
of the melting-points themselves. 

The molecular volumes of compounds at the melting-point 
cannot thus be utilized in the same way as those at the boiling- 
point. 

General Conclusions. 

A number of striking relations have been made out from a 
study of the open chain hydrocarbons, saturated and unsaturated, 
and some of the derivatives of the normal paraffins. These in¬ 
vestigations, while intrinsically interesting, do not cover sufficient 
ground to enable us to draw up a list of rules which might be 
of use in the study of compounds of unknown structure. More¬ 
over the nature of the limitations of the additive rule are not 


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i6 


LIQUID CHEMICAL COMPOUNDS . 


clearly understood, even in open chain normal compounds. 
Still less is this so in the case of compounds of more complicated 
structure, such as ring compounds. This must be ascribed to 
the highly constitutive nature of the melting point, a feature 
which would be likely to make the elucidation of the constitutive 
influences acting on molecular volumes at present a difficult 
matter. The results obtained, however, show, that in some cir¬ 
cumstances, additive relations may be clearly revealed, and what 
is important to remember, the relative volumes of the atoms 
are similar to those at the boiling-point. The following table 
contains a list of the chief results obtained. 


TABLE XI.— Table of General Results. 


40>4 


Atom or Linking. 

Value. 

Atom or Linking. 

Value. 

C 

n-88 4 [H] 

- CH : CH 2 | = | 

- 2*56 

H 

2*970 

-c ; ch - |=| 

- 3*20 

O' 

5*940 2[H] 

-c : n - i=i 

- 2-97 

O" 

8*910 3 [H] 



N"' 

8 910 3[H] 




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CHAPTER II. 

A STUDY OF THE HYDROCARBONS AT THE BOILING-POINT. 

The Open-Chain Hydrocarbons. 

The Volume of Carbon and Hydrogen . 

These atoms are of fundamental importance in a study of the 
molecular volumes of organic compounds, and as such demand 
careful consideration. This is especially necessary in view of the 
fact that Kopp’s numbers 11 are unreliable. 

We may follow his line of reasoning, by a study of the 
compounds butane C 4 H 10 and benzene C a H 6 , according to his 
method. Thus:— 

[C 4 H 10 J = [C 6 HJ = 96-0 . . . (i). 

It was also shown that 

[CHJ = 22*0 . . . (2). 

From (i) we conclude that [C] = 2[H], and applying this to 
(2), we find that 

[C] = iro and [H] = 5*5. 

The compounds butane C 4 H 10 and benzene C a H a , and also 
those actually studied by Kopp, belong to two entirely different 
classes of chemical compounds, and are possessed of quite 
different structures. Butane is an open-chain compound and 
benzene possesses ring structure. It is thus not necessarily true 
that similar atoms, are identical in volume, in the two classes 
of compounds mentioned. This was the assumption Kopp made, 
and, as we shall see, it was not justifiable. 

The most direct way of showing this would be to ascertain 
the volume of dipropargyl C a H a , a compound which has a struc¬ 
ture similar to that of butane and a composition similar to that 
of benzene. Its molecular volume has not been directly deter¬ 
mined, but the probable value can be obtained quite easily, 
from a study of the available data for the unsaturated hexane 
derivatives. 

17 2 


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LIQUID CHEMICAL COMPOUNDS. 


TABLE XII. 



Compound C 6 . 

Vm. 

»H,. 

Hexane 

CH, . CH, . CH, . CH, . CH, . CH, 

139*9 

7*5 

Hexylene 

CH, . CH, . CH, . CH, . CH : CH, 

132*4 

2 x 6*9 

Diallyl 

CH, : CH . CH, . CH,. CH : CH, 

126*1 

4 x 7*4 

Dipropargyl CH : C . CH, . CH, . C j CH 

[n°'3] 


The first three compounds have been directly investigated; 
the fourth value is found by extrapolation, assuming the validity 
of the summation law. 

The volume of dipropargyl:— 


CH : 0 . CH, . CH, . C : CH is 110*3. 
The volume of benzene 


CH 

^ \ 

CH CH 


is 96*0 


:h ch 

\ / 

CH 


- 14*3 


We conclude, that the volumes of similar atoms, are not the 
same in the two compounds, nor in the two classes of com¬ 
pounds, and consequently Kopp’s assumption is unjustified. It 
is seen that on passing from open to closed-chain structure, there 
is a large contraction of - 14*3 which must be accounted for. 

The next step, is to show what the actual values of carbon 
and hydrogen in paraffin and benzene derivatives are. 

If we take the same two compounds—butane and benzene— 
into consideration, and for the moment, suppose that the volume 
represented by [C*H c ], is that of benzene, but with its atoms 
similar in volume to those of dipropargyl, then— 

[C 6 HJ - 4[H] = 96*0. 

But [C 4 H 10 ] =s 96*0. 

It follows, that [C 4 H 10 ] = [C e HJ - 4 [H] 

and thus [C] = 4 [H] . . . . . (1) 

But [CHJ = 22*2.(2) 

Therefore [C] = i 4 *7 and [H] = 37. 

It is interesting to note that the relation [C] = 4[H] is the 
same as that which was also found to be true at the melting- 
point 


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HYDROCARBONS AT THE BOILING-POINT 19 

The values [C] = 147 and [//] =37 are the actual atomic 
volumes of combined carbon and hydrogen at the boiling-point 
probably in all compounds with open-chain structure . At any 
rate we must consider them to be the normal values . 

The conclusions of contemporary writers were not always 
the same as those of Kopp, for Lothar Meyer advocated a value 
of 3*0 for hydrogen, and Loschmidt came very near to anticipat¬ 
ing the true values by the numbers [C] = 14*0 and [H] = 3*5. 

The benzene difficulty was got over by assuming that the 
volume of each of three carbon atoms was equal to 11 *o, and that 
of each of the other three 14*0. The volumes of the hydrogen 
atoms were given as 3*5. 

Reverting to the numbers which are now proposed for com¬ 
bined carbon and hydrogen, we see that they stand in the 
relation of 4 :1. 

It can be shown that on passing from butane or dipropargyl 
to benzene the relation already indicated is preserved unimpaired. 

Thus, at the critical point, the volumes of carbon and hydro¬ 
gen are 

[C] = 387 and [H] = 9*67 

among the paraffins—values which are as 4: 1. 

For ring compounds, a different result is obtained. 

Benzene [C 6 HJ = 256*3 
Hexamethylene [C 6 H 12 ] = 306*7 

A for 6[H] 50*4 = 6 x 8*40 

6[C] = 256*3 - 50*4 = 205*9 
and [C] = 34*3 or 4 x 8*57, 

[H] » 8*40. 

These values are also approximately in the relation of 4: 1. 
By assuming this relation to be true, and dividing the critical 
volumes of benzene and hexamethylene by the respective valency 
numbers, we obtain nearly constant values for V^/W, which values 
represent the volume of hydrogen. 


v c w. v c /w 

m ml 

Benzene C 6 H 6 256*3 30 8*54 

Hexamethylene C 6 H 13 306*7 36 8*52 


The 4: 1 rule may be shown to be true, not only at the boil¬ 
ing and critical points, but also at all equally reduced pressures. 

2 * 


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20 


LIQUID CHEMICAL COMPOUNDS, 


We conclude from this, that on passing from the aliphatic to 
the aromatic class of compounds, the volumes of the carbon and 
hydrogen atoms undergo a contraction, but in such a way as to 
preserve the characteristic numerical relation unimpaired The 
total contraction for benzene and the other ring compounds is 
equal to the sum of the contractions of all the atoms in the 
nuclei. 

TABLE XIII.— Direct Investigation op the Atomic Volumes op Carbon 
and Hydrogen. See Le Bas (loc. cit.) and ref. 12 


Substance. 

Vw. 

C 6 H u 

117-8 

C.H 14 

139-9 


2[H] = [C 5 H,J - 5[CHJ = 117-8 - 5 x 22-i = 7-3 (2 x 3-65) 

[C] = 22-i - 7-3 = 14-8 (4 x 3-70). 

The above results are thus in favour of the average atomic 
volumes already given—[H] = 370 and [C] = 14/8, and the 
evidence seems to be indisputable. The result of such evidence 
is to completely invalidate the original numbers of Kopp. 

Those which have just been obtained, are, however, also sup¬ 
ported by a comparison of the volumes of certain normal paraffins, 
olefins, diolefins, etc. 

TABLE XIV. —The Atomic Volume op Hydrogen. 


Substance. 

Vm, 

»h 2 . 

Vm. 

Olefin. 

C»H la 

117-8 

77 

iio-i j 

c 5 h 10 

— 

— 

2 x 6*7 

104*5 


C,H 14 

139*9 

7*5 

132*4 

C,H la 


— 

2 x 6-9 

126-1 

C,H 10 

c*h 7 ( 0 H) 

81-5 

7*3 

74*2 

CjH s (OH) 

C,H,C 1 

917 

7*3 

84-4 

C s H 6 C 1 

N(C3H,) 3 

222*4 

3 x 7-2 

200*7 

N(C s H 5 ) 3 


Mean value of [H] a = 7*15 




A similar result is obtained from a consideration of the 


volumes of ethyl benzene, and its unsaturated derivatives. 


Compound. 


Vm. 

C,H t . 

CHj. 

CH S 

139*3 

c,h b . 

, CH 2 

CHj 

131*5 

c,h 5 . 

C : 

CH 

126*2 


A for nH a . 

7-8 
2 x 6-6 


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HYDROCARBONS AT THE BOILING-POINT 


21 


The above compounds are for the most part unsaturated, 
but similar results can be obtained from a consideration of 
saturated ones. Thus— 


H 

H 


COOCH3 

COOCH3 


= H« 


COOCHg 

Aooch* 


Two molecules of methyl formate. Dimethyl oxalate. 

2[H] = a[H . COOCHJ - [(COOCH,)J = 125-0 - 117-4 = 7’6. 


It follows from the above calculations that the average 
volume of combined hydrogen in organic compounds is— 

[H] = 370. 


TABLE XV.— The Atomic Volume of Carbon. 


Substance. 

Vm. 

A for Carbon. 

Vm. 

Olefin. 

C 4 H 10 

96*0 

14*1 

110*1 

C 6 H io 


117*8 

14*6 

132-4 

C,H U 

c,h 14 

139*9 

14*9 

i 54'8 

c,h ]4 

C,H 16 

162*6 

15*0 

177-6 

c 8 h 16 

Mean value of carbon [C] = i4*6 




The average volume of carbon, taking all the data into con 
sideration, is— 

[C] - 14*8. 

The volumes of combined carbon and hydrogen given above, 
are average ones only, and, as such, are of no special significance. 
They are, however, useful for purposes of calculation. 

If we except liquid hydrogen itself, and perhaps methane, the 
combined volume varies within the comparatively narrow limits 
of 3-4, even including compounds of widely different structure. 

Note on the Effect of Unsaturation at the Boiling-point. —A note 
is required on the result which has been obtained for unsatura¬ 
tion. It is seen that the values for corresponding members of 
the n paraffin, olefin and acetylene series are simply dependent 
on their composition. There is thus no special effect due to 
unsaturation at the boiling point . The evidence for this conclu¬ 
sion is so strong that it is scarcely open to question. 


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22 


LIQUID CHEMICAL COMPOUNDS. 


Very different results have previously been obtained by 
different observers. Buff 13 , in 1865, sought to show that carbon 
possesses greater volume in unsaturated than in saturated com¬ 
pounds. This was apparently confirmed by Schiff, 14 who calcu¬ 
lated that the increase for single unsaturation, was 4 0 units, 
approximately. Thus— 

v w . 

Amylene C 5 H 10 no*o 

Pentane C 5 H 12 117*2 

A = 7*2 

Then if H 2 = 2 x 2*55 

1 = 1 = n*o - 7*2 = + 3*8. 

Lossen 16 thought that this increase was due to the hydrogen 
rather than the carbon. 

These results are evidently due to the particular atomic 
volumes of hydrogen and carbon chosen. 

If we grant the validity of the new numbers, the obser¬ 
vation, that unsaturation is responsible for no special effect, follows 
as a matter of course. 


The Influence of Complexity on Molecular Volumes , especially that 
connected with the Influence of the Homologous Increment . 

It has been repeatedly stated that the additive rule is not 
quite followed in molecular volumes. This was first shown by 
Gartenmeister, 16 Dobriner, 17 Schiff, 18 Pinette, 19 Zander, 20 and 
others, from the study of the compounds of various homologous 
series, that is, compounds which differ in constitution by the 
group methylene (CH 2 ). The series in question are those of the 
ethereal salts of the fatty acids, the ethers, the alkyl iodides, etc. 

More recently, Young 21 has shown, that, under a variety of 
conditions, the normal paraffin series of compounds, always differ 
from term to term when the group CH 2 is added. Thus, under 
no circumstances, is the additive rule exactly realized. 

The differences in volume between two successive terms of a 
series, have, however, been shown to give unreliable information 
regarding the extent to which the additive rule is departed from. 
The accompanying table shows this. 


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HYDROCARBONS AT THE BOILING-POINT 


23 


TABLE XVI. —The Volumes of the n Paraffins at the Boiling and 
Critical Points. 


Substance. 

W. 

V m 
at the 
boiling- 
point. 

A. 

v m /w. 

v*. 

m 

A. 

v e 

m 

W* 

n Butane C 4 H 10 

26 

96*0 


3-693 

251*0 


9-654 




21*8 



58*3 


n Pentane C 6 H 12 

32 

117*8 


3-681 

309-3 


9-666 




22*13 



56*8 


n Hexane C 6 H 14 

38 

I 39*93 


3-682 

366*1 


9-634 




22*63 



6o*2 


n Heptane C 7 H 16 

44 

162*56 


3*693 

426*3 


9-689 


If we take into consideration the fact that in the aldehydes 
the volume of oxygen is equal to twice that of hydrogen, and 
that, so far as a comparison can be made, the members of the two 
series possess almost identical volumes, we do not perhaps com- 
mit any very serious error, if we suppose that the volumes of the 
simplest paraffins, are similar to those of the aldehydes, which 
have been investigated. 

TABLE XVII. —The Volumes of the Normal Paraffin Series.” 


Substance. 

w. 

V w . 

Vm/W. 

ch 4 

C.H, 

8 

38-5 

4*812 

14 

56-7 

4*050 

c,h 8 

20 

74-6 

3*730 

c 4 h m 

26 

96*0 

3*693 

C 5 H la 

32 

117*8 

3*681 

C.H„ 

38 

139*93 

3*682 

CtH 16 

44 

162*56 

3*695 

c„h 18 

50 

186*26 

3*725 


The curve shown on next page is similar to those obtained for 
many series and indicates the variations in the volume of combined 
hydrogen in the series. It consists of three parts:— 

(а) A descending arm : This shows that the volumes of 
hydrogen diminish rapidly from compound to compound. 

( б ) A minimum: The volumes of hydrogen are a minimum at 
this point. For a limited range of complexity the atomic 
volumes do not differ much. It is to this circumstance that the 
approximate additive relations which have been noted, are due. 

(c) An ascending arm: The values of V/W increase, possibly 
in a rectilinear way. 


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24 


LIQUID CHEMICAL COMPOUNDS . 


The influences which contribute to the above result, are not 
quite clear, but we are probably correct in supposing that several 
are operative, The following explanation seems to be at least 
plausible. We suppose, that, at any rate, the following two 
influences are probably important: (a) the influence of the element 
carbon with its enormous power of self affinity; ( b ) and the effect 
of the volatile hydrogen with its large molecular volume. These 



Fig. 1. 

characteristics are not lost in combination. It follows, that the 
volume of methane, might be expected to be relatively large, owing 
to the large proportion of hydrogen atoms present in the mole¬ 
cule, compared with the number of carbon atoms. As methylene 
groups (CH 2 ) are added, the proportion of carbon increases, and 
thus there is a very considerable diminution in the values of 
V m /W. The reason for the ultimate increase in the value V m [W 
is not quite so clear. This possibly is owing to a gradually 
changing relation of the volumes to the boiling-points, which also 
involves the magnitude of the internal pressures due to the 


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HYDROCARBONS AT THE BOILING-POINT. 


25 


intramolecular forces. Thus in general terms, we suppose that the 
intramolecular and consequently the intermolecular forces are 
different among the different compounds of a homologous series, 
so that the molecules are freed at temperatures which do not 
preserve the necessary volume relationships which make the 
compounds completely homologous. The extent by which they 
differ indicates the constitutive differences between them. Young 
attributes these variations to constitutive causes. 

The Branching of the Hydrocarbon Chain . 

This is the only constitutive influence likely to affect the 
volumes of the open-chain hydrocarbons, since unsaturation does 
not cause any special effect. The data are, however, very meagre, 
so that the conclusions have not that proved generality which is 
desirable. 

The iso structure seems to cause a definite lowering of the 
boiling-point (8-9 degrees), and a definite contraction (0*50). 

TABLE XVIII. —Contraction for the Iso Group. 


Normal Compound. 

Vm. 

Iso Group. 

V w . 

Iso Compound. 

n Pentane C 6 H 12 

117*8 

- 0*40 

117*4 

(CH s ) a . CH . CH a . CH, 

n Hexane C 8 H l4 

139*9 

-0*50 

139*4 

(CH 3 ) 2 . CH . CH 2 . CH 2 . CH, 

n Heptane C 7 H 16 

162*9 

-o*6o 

162*3 

(CH s ) 2 . CH . CH,. CH a . CH 2 . CH 3 

n Octane C 8 H J8 

186*6 

- 0*90 x 2 

185*2 

(CH 3 ) 2 . CH . (CH a ) 2 . CH, . (CH 3 ) 2 

Valerylene C 5 H 8 

104*2 

-0*30 

103*9 

Isoprene 


A = 

- 0*53 




The contractions due to the presence of the iso group, seem 
to increase with complexity, and the average value is about 

(Iso group) 0*50. 

The observed contraction, which is characteristic of com¬ 
pounds with the iso group, is no doubt associated with a greater 
concentration of matter at the point at which this group is 
situated, than at other points in the molecules. This is shown 
by the following scheme— 


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26 


LIQUID CHEMICAL COMPOUNDS, m 


(i) 


C 



C 

The iso group. 


( 2 ) —C—C—C—C—C— 


Normal chain structure. 


The contractions which have just been indicated, illustrate 
that great capacity for self-affinity which characterizes carbon, 
and which is most effective when the atoms are most concentrated. 
It is possible that the large contractions which distinguish ring 
structure, may be due to this cause. This more compact arrange¬ 
ment, affects not only the carbon, but the hydrogen atoms also. 

Naumann 23 in 1874 stated the following rule for the boiling- 
points of the paraffins and other open-chain hydrocarbons: “ The 
more nearly the grouping of the atoms in an isomeric paraffin 
deviates from the rectilinear or chain type> and approaches the 
spherical type y the lower is the boiling-point 

A similar rule, moreover, may perhaps apply to the mole¬ 
cular volume, that is, so far as observation goes, and the rule 
may have as great generality for volumes as for boiling-points, 
provided we limit it to the various hydrocarbon series. 


The Interaction between Methyl Groups . 

The average value of the contraction for an iso group is 
-o*5, and one of about twice the magnitude may be deduced 
from the volume of di-isobutyl which contains two iso groups. 
For di-isopropyl, where the iso groups are nearer to each other, a 


much larger contraction is noticed. 


Di-isobutyl. 

c 8 h 18 

Di-isopropyl. C 6 H 14 

ch 3 

CH, 

CH, CH 3 


d:H—CH 3 —CHa—CH CH—CH 

ch 3 ch 3 ’ ch 3 Ah 3 


A - 1*4 (2 x - 07). 

A -3*1. 

Vm 185*2. 

136*8. 


The magnitude of A in di-isobutyl is equal to the contraction 
caused by two iso groups acting independently, but this double 
value is augmented in di-isopropyl, owing to the closer approxi¬ 
mation, and consequently probable interaction of these groups. 
The augmentation in question, is— 

- (3*1 - 1*4) - - 17. 


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HYDROCARBONS AT THE BOILING-POINT. 


27 


The real cause of the above contraction is considered to be 
due to the interaction of CH 3 groups attached to different carbon 
atoms. This is evident from the diminished boiling points. 


If we consider a compound in which an iso group and an 
ethenoid linkage are close to one another, we shall notice a 
disturbance in the total value of the constitutive effect. 


v m . 

n Amylene 
C 3 H 7 - CH = CH a 

110-5* 

* [This value has been calculated by subtracting 7*3 from the molecular volume 
of pentane Vm = 117*8.] 


A - 0*40 This is about equal to 
one iso group. 

iio*i (Sch.) 

A - 2*40 

108*1 (Th.) 

CH 8 

Reasons are given later on for supposing that the above con¬ 
traction is due to the interaction of two CH 3 groups. This 
necessitates a modification of the above formula, thus— 

CH 8 — c -CH 8 

11 

CH—CH 8 

Other compounds of this type are studied later on. The rule is 
that when two methyl groups (or four) are attached to neighbouring 
carbon atoms there are contractions due probably to interaction 
between these groups. 

In the foregoing account, we have dealt entirely with the 
influence of the iso group, but of course, a hydrocarbon chain 
may be divided up in different ways. 


a Amylene 


CH 8 

^H- 


CH = CH, 


0 Amylene 
CH 8 

i = 


CH - CH, 


The Influence of the Tertiary Grouping on Volume. 

Doubtless the grouping (CH 3 ) 3 C - would show an increased 
contraction, as compared with an iso grouping, but actual data 
are lacking for the hydrocarbons. The volume of pinakolin 
(CH 3 ) 3 . C . CO . CH 3 is 138*6, and if the volume of 0 " be equal 


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28 


LIQUID CHEMICAL COMPOUNDS. 


to 2H, as is usual in such compounds, then the volume is equal 
to that of trimethylethyl methane (CH 8 ) 8 . C—CH 2 —CH 8 . 


Trimethyl methane. 
CH, 

CH,—i—CH,—CH, 

(!h, 

V» i 3 8 -6. 


Pinakolin. 

CH. 

-<U 

<1h, 

138*6 


The volume of the hydrocarbon, is thus, about 138 *6, a value 
which is less than that of normal pentane by 139*9 - 138*6 
= I *3. This value is,— 

a = -1*3 = - 0*65 x 2, 

or the contraction due to this tertiary group is twice that for an 
iso group. 

In some of the compounds at any rate, the contraction may 
be due, in part at least, to an interaction of groups attached to 
different carbon atoms. This is seen to be possible if we give to 
trimethyl methane and pinakolin the following configurations— 


CHo 


V 


j X CH s 

CH* 


CH 3 


CH, 



CHj CH 3 


Trimethyl methane. 


Pinakolin. 


This possibility is lost sight of in the plane formulae, but the 
solid models or diagrams to represent them, would show this. 
This fact may be explained as follows :— 

If we suppose, that, in the iso and tertiary groups, one CH 3 
group is continuous with the main chain, then the other CH 8 
group in the iso arrangement, and the other two CH 8 groups 
in the tertiary, respectively occupy the $ positions, as shown in 
the subjoined schemes. 


I so Group. 


CH 8 —CH—CHa— 

ch 3 

A = - 0*50 


Tertiary Group. 

CH, 

CH;,—C—CH,— 

c!h, 

A = - 1*3 = 2 X - 0*65 


The CH a groups, in effect, substitute hydrogen atoms from the 
yS position, like chlorine or other atoms would, and consequently 
the CH 8 groups occupy similar positions to the latter in the 


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HYDROCARBONS AT THE BOILING-POINT 


29 


molecule. It consequently represents two propane residues, 
joined together by their middle carbon atoms. 

These formulae are similar to those upon which the “ Geneva 
Commission” has based its system of nomenclature, and the 
formulae suggested by it would seem to have theoretical justi¬ 
fication. 

The formula for di-isopropyl, taking into consideration the 
contraction is 



Unsaturated Compounds. 

In studying the hydrocarbons, it will be of great advantage 
to consider the branching of the chain as equivalent to substitu¬ 
tions of the methyl group for hydrogen. Moreover, if more 
than one substitution has taken place, the distribution may be 

(а) Unsymmetrical CHX*. CH g 

CX*: CH a 

(б) Symmetrical CH,X. CH*X 

CHX:CHX 
CXj-.CX* 

These features will affect both the molecular volumes and the 
boiling-points of the compounds. 

The following rules have been made out:— 


CH S group 
Cl 


Unsymmetrical Distribution. 


(CHj) 2 CH - AV - 0*5 
(CH S ) S C- AV-ro 
Cl* CH - 

Cl 8 C - AV + i-5 
Cl 4 C AV + 3*0 


b.p. - 8*o 
- 28*0 

gradually diminishing differ¬ 
ences for Cl-H, showing 
depression with continued 
substitution. 


Symmetrical Distribution. 

CH 8 group - C(CH S ) • C(CHj) - AV - 1*5 to - 3*1 b.p. + 5*0 

Cl - CHC 1 . CHC 1 - 31 + 23*6 

- CHBr . CHBr - - 3*1 + 20*3 

The following olefins are normal, or nearly so:— 


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30 LIQUID CHEMICAL COMPOUNDS. 



Mono-Olefins. 

Vm 

V of sat. 
compd. 

less n x 7* 
or 2 n Va 

£ Amylene 

CH 8 . CH 2 . CH : CH . CH 8 

IIO*I 

117*8 

110*4 

a Hexylene CH S . CH 2 . CH a . CH 2 . CH : CH 2 

132*4 

139*9 

132*5 

a Heptylene CH 8 . CH 2 . CH 2 . CH 2 . CH 2 . CH : CH 2 

154*8 

162*6 

155*2 

a Octylene 

CH 8 . (CHJj. CH : CH 2 

177*6 

— 

176*8 


Di-Olefins. 




Isoprene 

CH 2 : CH. C(CH S ): CH a 

103*6 

— 

— 

Diallyl 

CH a : CH. (CH 2 ) 2 . CH : CH a 

125*1 

I39’9 

125*1 

Aromatic unsaturated compound. 




Styrolene 

C 8 H 5 .CH:CH 2 

131*4 

139*3 

131*9 


The following olefins are abnormal:— 

Pseudo butylene (dimethyl ethylene) symmetrical compound. 
CH s .CH:CH.CHj b.p. + i° 

b.p. of a compound - 5° 

For CH S groups in a & pos. + 6 


Calculated b.p. + i° 

valerylene - <*13 0*653 (Chem. kal.) A = 0*00075. 
d i 0*^53 + 12 x 0*00075 = 0*644 V m 86*9. 

2 nV a — 96*0 - 7*4 = 88*6. 

A = Vm - = 86*9 - 88*6 = - 1*7. 

There is thus an increase in boiling-point for symmetrical 
distribution (6°) and a contraction of - 1 *7. 

Trimethyl ethylene (CH 8 ) 2 . C: CH(CH,) 
b.p. 36° Vm 108*1 (Thorpe). 

compare 

C(CH3) a :CH(CH s ) 

A = - 2*0 
with 

CCl a : CHC1 
A = - i‘5 
for contractions 


IIO*I 

and for trimethyl ethylene 108*1 
A = ~ 2*0 

The contraction - 2*0 is connected with the symmetrical 
distribution of the methyl groups. 

Di-isopropyl. 

CH(CH 8 ) 2 . CH(CH 8 ) 8 
b.p. 58*0 

b.p. n C 8 H 14 71 0 

less two iso groups - 18 (2 x 9) 

calculated 53 

observed 58 

A = + 5 


b.p. of C 5 Hj h fi amylene 39 0 
corr. for iso group - 8 

3i 

for a £ const. + 5 

calculated b.p. 36 
observed 36 

Since the volume of 

a or £ amylene is Vm 


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HYDROCARBONS AT THE BOILING-POINT. 


3i 


There is thus an increase above the expected value. This 
result is no doubt due to the interaction of neighbouring iso 
groups. Also— 

V m 136*8 
2 nVa 139*9 


A= - 3*1 

The contraction for this compound is thus -3*1 below the 
normal. 

The following example from among the aromatic compounds 
will help us to solve the problem of the constitution of these 
compounds. 


0 xylene 


/ c \ 



b.p. 

Vm 

CEL C— 

—och 3N 

0 xylene 

141-9 

137*9 

fl 

\ 

1 

1 

p xylene 

138-9 

140*2 

II 

CH 

—CHs ''' 

A 

_+T 9 

-2-3 


There is thus an increase in the boiling-point of +3*9, and a 
contraction of - 2*3 owing to the approximation of the methyl 
groups. 

A further study of the tri- and tetra-methyl benzenes shows 
results which are similar. 


Sym. dimethyl ethylene 

AV 

b.p. 

CHj.CHjCH.CH, 
Trimethyl ethylene 

- 17 

+ 6° 

(CHj) 8 C:C(CH 8 ) 
Tetramethyl ethylene 

- 2*0 

+ 5 ° 

(CH JjC: C(CH,) f 
Ditaopropyl 

- 4*6 

+ 14 ° 

(CHj) s CH. CH(CH,) 4 

0 Xylene 

- 3 *i 

+ 5 ° 

C*H,(CHJ, 

- 2-3 

+ 3-9 from p xylene 
+ 5*4 from ethyl benzene 


The formula for 0 xylene would be 


,CH=CH 


CH 


\ 



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32 


LIQUID CHEMICAL COMPOUNDS. 


and by analogy 


CH- 

CH- 


CU 3n 


for symm. dimethyl ethylene compare 

CH-CK 


-ch 3 ' 



CH- 


-Cl' 


acetylene chlor¬ 
ide (q.v.) 



Tetramethyl ethylene. 


CH 3 Cl- 



CH- 


-CK 

J 


Chlor ethylene 
chloride. 


-Cl 




'Cl- 


-Cl' 


Tetrachlor ethylene. 


Diisopropyl. 

CH 3 ch 3 

CH CH 


CH 3 ch 3 




In all these cases where there is an augmentation of the 
boiling-point and a diminution of the volume, there is spatial 
proximity of the CH 3 groups. We therefore conclude that the 
effect is due to an interaction of the groups. 

A convincing piece of evidence is found in an examination 
of the volumes of the di- and polyhalogen derivatives of the 
paraffins. 

The chlorine atom in propyl chloride (terminal) has a volume 
of 21 *5 and in isopropyl chloride (central) a volume of 24*3. The 
sum of the volumes of these two chlorine atoms is 45 *8. 

Propylene chloride which has one chlorine atom in the a 


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HYDROCARBONS AT THE BOILING-POINT . 


33 


position and one in the yS position has such a volume that the 
sum of the two chlorine atoms is apparently 41*6. There is 
thus a considerable diminution in volume caused by the presence 
of the two chlorine atoms in the same molecule, one in the a and 
and one in the # position. 


Closed-Chain Hydrocarbons. 

Aromatic Hydrocarbons and Ring Structure . 

There is a constitutive effect in these compounds which is due 
to ring structure, as already shown. Without going more fully 
into the question of the cause of ring structure at present, we 
simply calculate the values of SnV ai and express this correction 
as a negative difference. 

TABLE XIX.— Ring Hydrocarbons. 


Substance. 

.. .. . _ 

Vtn . 

2»Va. 

A, 

Diamylene . 


211*7 

220*3 

- 8*6 

Benzene 

• C 6 H 6 

96*0 

111*0 

- 15*0 

Toluene 

. C„H 6 . CH, 

118-3 

133-2 

“ 151 

p Xylene 

. C 6 H 4 (CH a ) 2 

140’S 

155*4 

- 14*9 

Ethyl benzene 

• c,h 6 c,h 6 

139*5 

— 

- 15*9 

Mesitylene . 

. C,H,(CH,) a 

162*8 

we 

- 14*8 

Propyl benzene . 

• C e HjC,H 7 

162*2 

— 

-15*4 

Cymene 

. C e H 4 (CH a )C,H 7 

1849 

199-8 

- 14*9 

Hexamethylene . 

• c,h 12 

ii6*3 

133-2 

- 16*9 

Hexahydrotoluene 

• C,H U CH, 

141*8 

155-4 

- 13*6 

Hexahydroxylene 

. C e H 10 (CH 3 )j 

164-3 

177-6 

- 13*3 

Naphthalene 

• CjoHg 

147-2 

177-6 

- 30-4 

Naphthyl hydride 

• c 10 h 14 

171*2 

200*0 

- 28*8 

Anthracene. 

• c 14 h 10 

195*5 

244*2 

- 48-7 


Simple Rings. 

Hotnologues of Benzene . 

Benzene C 6 H 6 Vtn 96*0 H 3*2. 

Vw. 

Toluene C 7 H 8 118*25 (Schiff) 

C 6 H 6 - CH S 

C 6 H 6 - 92*8 

3 


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34 


LIQUID CHEMICAL COMPOUNDS. 


A for CH, 25-45 [CH,] = 25-45. 

• p xylene C 8 H 10 

C,H 4 (CH,), 140-5 (S.) 

C,H 4 89-6 

A for 2CH, 50-9 [CHJ = 25-45. 

Ethyl benzene 

CjHj . C,H, 139-28 (S.) 

rC,HJ = 47-48 
In paraffins 48-0 

A - 0-5. 

Mesitylene C,Hj, 

C,H, (CH,), 162-67 (S.) 

C,H, 86-4 

A for 3CH, 76-27 [CH,] = 25-42 

In paraffins 26-0 and larger 
A - o-6. 

Propyl benzene 

C,H, . C,H 7 16216 (S.) 

[C s H 7 ] 69-36 
In paraffins 70*0 
A - o*6. 

The volume of CH 3 is evidently the same in all these com¬ 
pounds, and is slightly less than in those which have an open- 
chain structure. 

[CH,] (in the paraffins) = 25*9 

[CH,] (in aromatic side chains) = 25*5 



The groups C 2 H 5 and C 8 H 7 also show a contraction as 
compared with similar residues in open-chain compounds. The 
contraction is - o*6. 

This is probably to be accounted for in a similar way to that 
for the iso group. 

Thus we have— 



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HYDROCARBONS AT THE BOILING-POINT 


35 


The principle is not affected if we suppose that the paraffin 
residues are directed along a line which cuts the rings at right 
angles, or nearly so. This is equivalent to branching. 

The volume of cymene may thus be synthesized:— 

Cymene C 8 H 7 . C 6 H 4 . CH 3 
C 6 H 4 8g-6 

CH S 25*45 

C 3 H 7 69*36 

2»Va 184*41 

Vm 184*88 

p methyl ethyl benzene. 

C 6 H 4 (CH 3 ) (C 2 H 6 ) 
c*h 4 89*6 

CH 3 25*45 

C 2 H 5 47 * 4 ^ 

5»V a 162*53 

Vm 162*32 

There are thus slight differences both + and - in the re¬ 
sults from which it would appear that small quantities of impur¬ 
ity might have been present in SchifFs material. For example 
small quantities of the ortho modification in p methyl ethyl 
benzene would account for the result. These compounds are 
notoriously difficult to completely purify. 


The Effect of Self-Affinity between the Side-chains of 
Aromatic Compounds . 

It has been shown that in the open-chain hydrocarbons self- 
affinity is manifested by contiguous paraffinoid groups. 

The same effect is well shown by the various aromatic com¬ 
pounds which possess two contiguous hydrocarbon side chains. 
The data are due to Pinette (loc. cit.). 

The xylenes C 8 H 10 . 


Vm 

A 


C—CH, 

c— ch 3 

CH 

/ \ 

✓ \ 

s \ 

CH CH 

CH CH 

CH C—CH. 

1 II 

1 11 

1 II 

CH CH 

CH C—CH 3 

CH C—CH S 

\ / 

\ / 

\ / 

C—CH, 

CH 

CH 

para (i: 4) 

meta (i: 3) 

ortho 1(1:2) 

140-25 - 0-25 

140*00 

I 37’95 


Difference between o and pA = - 2*3 

3 * 


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36 


LIQUID CHEMICAL COMPOUNDS. 


Strictly speaking two possible geometrical isomers of ortho 
xylene should be accounted for, as perhaps also for the others. 
They are:— 


CH=CH 


CH, 


CH = CH 


/ 

\l 

/ 

CH 

c 

CH 



1 

CH-C 


\ 


CH 


-/I 

I CH, 
CH, 


<!:h, 

opposed. adjacent. 

These isomers are constructed according to the well-known 
fumaroid and malenoid types. If we examine the data carefully 
we shall find that they agree with those which might be expected 
to apply to the two forms. 


Table XX.—The Volumes of the Xylenes. 



Schiff. 34 

Pinette. 25 

Neubeck. 26 

Para 

v w . 

140*5 

b.p. 

136-5 

Vm. 

140*25 

b.p. 

138*0 

Vm. 

140*77 

b.p. 

138-4 

Meta 

140*2 

139*2 

140*1 

138-9 

140*1 

I39*i 

Ortho 

140*2 

141*1 

137*9 

1 

141*9 

138*2 

141*1 

A between o and f 

-0*3 


-2*3 


-2*07 



It is observable that, as we pass from the para to the ortho 
compound, there is, on the whole, an increase in the boiling- 
point, and diminution in the volume. Comparing the values 
given by the different observers, we find between the para and the 
meta modifications, differences which are of a minor character. 

It is to be observed in regard to the ortho compound, that the 
boiling-points are similar, whilst the differences between the 
volumes obtained by different observers, are far too great to be 
ascribed to accidental causes. Pinette’s value is supported by 
that of Neubeck. Schiff, on the other hand, was a chemist of 
well-founded reputation for care and accuracy, so that his value is 
at least entitled to equal weight. 

It thus seems that the two sets of values refer to different 
forms of the same compound. Moreover, the lower values differ 
from that which might be expected by an amount equal to 


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HYDROCARBONS AT THE BOILING-POINT, 


37 


about 2*5. This is a normal feature of ortho compounds, if we 
consider the data available, and has been accounted for by sup¬ 
posing that there is an interaction between the groups owing to 
residual affinity. The lower value would thus correspond to the 
“Adjacent” orthoxylene. 

CH=CH 

/ \ 

CH C 

% 

CH —C 

I CH, 

CH, 

V m = 138*2. 

Schiffs larger volume is similar to that for paraxylene, thus 
showing that the groups are independent and unable to interact. 
This therefore corresponds to the 


“Opposed” orthoxylene. 


CH, 


CH=CH I 

/ \l 

CH C 

CH —C 


SH. 


Vm= 140*2. 


On looking at the two formulae we see that there is every 
reason to expect two forms. l 

A study of other derivatives of benzene shows similar peculi¬ 
arities to those already noticed. 

In the first place we must note the characteristics of “ ad¬ 
jacent 99 and “ opposed ” varieties of a compound. (See App. II.) 


The esters of maleic and fumaric acid. 


Maleate. 

Methyl. b.p. 208° 
Ethyl. 225 

Maleic. 

CH = CH 

ioocH s £ooch 3 


A Fumarate. 

+ 16*0 192 0 

+ 7*0 218 

Fumaric. 

COOCH, 

I 

CH = CH 

ioocH, 


Similar observations are made in the case of benzene de¬ 


rivatives. The ortho variety is usually some degrees higher in 
boiling-point than the para, and this we believe to be due to a 
conjunction of groups. 


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3 « 


LIQUID CHEMICAL COMPOUNDS. 


b.p. 

p xylene 
138° 

m xylene 

139° 

0 xylene 

142 0 

J 

b.p. 

para 

172 0 

v 

+ 4 ° 

Dichlorides. 

meta 

172 0 

ortho 

179 0 

j 

b.p. 

para 

219 0 

V_ 

+ 7° 
Dibromides. 

meta 

219 0 

ortho 

224 0 

_ j 

+ 5 ° 

The above and other data show that the meta is similar to 


the para, but that the ortho is some degrees higher. 

So we have shown that there is a difference in volume of 
about - 2*0, 


We, however, find apparent exceptions to the above rule. 

The chlor toluenes. 

para 

b.p. 


b.p. 


para 

163° 

meta 

- 13*0 150 + 6° 

ortho 

156° 


- 7° 



The brom toluenes. 


para 

meta 

ortho 

184° 

183° 

181 0 


— 3 


These anomalous results, where not due to association, may 
very well be the result of stereo isomerism. 

We inquire further into the question of the volumes of the 
hydrocarbon di- derivatives of benzene. 

The methyl ethyl benzenes. 

-ch 3 \ 

S C-CH2-CH3'' 


C—ch 3 

c-CH 3 

c- - 


/% 

y\ 

CH CH 

II 1 

CH CH 

11 I 

CH C 

II 1 

<1h <1h 

II I 

CH C—CH 2 .CH 8 

1 1 


\ ✓ 

C-CHj.CH 8 


b.p. 

Vm 


\ ✓ 

CH 

para 

162° 

162*3 


meta 

159 ° 

1607 


"V" 

ortho 

159 ° 

160*6 


A - 17 

Propyl benzene C 8 H 5 . CH 2 . CH 2 . CH S b.p. 158*6 Vm 162*2. 

The difference in volume between the ortho and para methyl 
ethyl benzenes is 

A = 160*6 - 162*3 = - 17. 


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HYDROCARBONS AT THE BOILING-POINT 


39 


From the fact that the volume of the para variety and the 
volume of propyl benzene are almost identical, we suppose that 
the methyl and the ethyl groups are independent, but from the 
fact that there is a diminution of - i *7 in the case of the ortho 
variety, we conclude that the groups interfere with each other. 
They are on the same side of the ring and the compound is thus 
of the adjacent type 


The methyl propyl benzenes. 

C-CH, C-CHg C-CHg 






CH CH 

CH CH 

CH C— 

CH 2 .CH 2 . 

II 1 

CH CH 

II 1 

CH C—CH,.CH,.CH, 

A L 


\s 

W 

\s 


C—CH,.CH,.CH, 

CH 

CH 


para 

meta 

ortho 


b.p. 175*0 177 

182*0 


M 

s 

M 

00 

£ 

H 

>* 

— 


Butyl benzene 

C,H,CH,. CH,. CH,. CH, 

b.p, 180 

V*> 184*8 

Iso butyl benzene 

CH, 

C,H,.CH,.CH<^ 

b.p. 167*5 

Vm 1777 

Secondary butyl benzene 

CH, 

C,H,. CH. CH,. CH, 

b.p. 171 0 

Vm 181*4 


CH, 


These last two compounds illustrate the rule that when un¬ 
saturated groups are attached to the benzene nucleus, large 
contractions in volume are apparent. 


The methyl isopropyl benzenes. 


C-CH S C-CH, C-CHg 





/ \ 

CH CH 

II 1 

CH CH 
11 1 

CH, 

CH C—CH 
II 1 

CH CH CH , 

CH C— 

CH<^ 

CH, 

i:H CH 

\S / 

\S 


C-CH<^ 

CHg 

CH 

3 

CH 

para 


meta 

ortho 


CH, 

/ 

\ 

CH, 


b.p. 171 176 — 

Vm 184*8 183*6 — t 

A b.p. between para and meta 176 - 171 = + 5 0 

A Vm between para and meta 183*6 - 184*8 = - i*a 


It is remarkable that whilst there is no distinction between 
the para methyl n propyl and methyl isopropyl benzenes as 
regards volume, the meta normal compound shows a small com¬ 
pression and the meta iso compound shows a larger compression. 


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40 


LIQUID CHEMICAL COMPOUNDS, 


Diethyl benzene. 
C-CH 2 • CH. 

CH CH 


L L 


\ s 

C-CHj.CHg 

b.p. 179 0 Vm [185*4] 0*8707 C 0*520. 

C 6 H 4 89*6 
2C g H 5 96*0 

185*6 
Vm 185*4 


b.p. 


Tri substituted benzenes. 
The trichlor benzenes. 
1:3:5 1:2:4 

208 213 


: 2 :3 
218 


C— 

CH CH 

II I 

CH 8 -C C—CH 

W 

CH 

Mesitylene. 

1:3:5 
b.p. 164*5 


+ 5 2 x + 5 

The trimethyl benzenes. 

CH s ,c-—ch 3 


/ \ 

CH CH 


CH 

\ 


-CH 3 ', 

c— —ch 3 ) 

Pseudocumene. 

1:3:4 

170 

_/ V_ 


:ff\ 


-ch 3 


-ch 3 ; 




-CH S / 


CH 

Hemimellithene. 

1:2:3 

175 


+ 5*5 


+ 5 


V*n 162*8 


[160*9] 


- 1*9 


We see that there is an increase in temperature of + 5 0 for 
each step of the change from mesitylene to hemimellithene, and 
a contraction of - 1 *9 from mesitylene to pseudo cumene. We 
cannot doubt that the volume of hemimellithene would be 
162*8 - 2 x i*9= 159 0 at least. 


The tetramethyl benzenes. 


CH 


/\ 

TT Vi 


ch 3 


•CH 3 ' 




CHs 


.''CHs C \ 

v CHs——X j 


CH 


CHs-C, 




-CHs'. 


-CHs' 


CH 


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HYDROCARBONS AT THE BOILING-POINT 


4i 


Prehnitol. 

204*0 


Vm 184*4 

180*0 = io*o = 2x5° 
180*0 = 16*0 = 2x8° 
180*0 = 24*0 = 3x8° 

We thus see that two independent ortho groups occasion a 
rise in the boiling-point of twice that for a single ortho group. 
Two contiguous ortho groups occasion a rise of twice 8° and 
three contiguous ortho groups a rise of thrice 8°. 

The two contiguous ortho groups of isodurene cause a con¬ 
traction A = 184-4- 181*8 = - 2*6 = 2 x - 1*3. 

In reviewing the work done in the last section we note that 


whenever two methyl groups 

; are 

in association there are 

augmentations of + 5° 

in the 

boiling-point and contractions of 

- 17. 




Examples. 

A. 

A. 


p xylene 

140*3 

- 2*4 

one ortho 

0 xylene 

137*9 

p methyl ethyl 

162*3 

- 1*7 

one ortho 

0 methyl ethyl 

160*6 

1:3:5 trimethyl 

162*8 

- i *9 

one ortho 

1:3:4 trimethyl 

160*9 

1:3:5 dimethyl ethyl 

184*8 

- i*6 

one ortho 

1:3:4 dimethyl ethyl 

183*2 

Tetramethyl calculated 

1:2:3 :5 tetramethyl 

185*2 

181*8 

- 17 X 

2 two ortho groups (contiguous) 


/V CH3 ^ 

ch t:-ch 3 ; 


CH 3 v 
/ 




Durene. 
b p. 190° 
Vm — 


C--CHa 

Isodurene. 

196*0 

[181*8] 


Butyl benzene. 

C 6 H 5 . CH 2 . CH a . CH 2 . CH 3 b.p. 180*0 

A b.p. between butyl benzene and durene 190*0 - 

A b.p. between butyl benzene and isodurene 196*0 - 

A b.p. between butyl benzene and prehnitol 204*0 - 


It is thus concluded that whenever we have two methyl 
groups in conjunction there are contractions of -1*7 or there¬ 
abouts, and as often as this is repeated in a single molecule, we 
find this contraction. 

From this it follows that those compounds which have been 
examined are the “adjacent” varieties and the formulae of these 
would be 


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42 


LIQUID CHEMICAL COMPOUNDS. 



o xylene. o methyl ethyl. 1:3:4 trimethyl. 1:3:4 dimethyl ethyl. 

If the substituents be methyl groups, they are unable to 
interact when in the meta position relatively to each other, but 
there are indications that when the chain is lengthened they may 
do so. 


V*». A. 

p methyl ethyl benzene 162*3 _ i*( 

m methyl ethyl benzene 1607 

p methyl isopropyl 184*8 

m methyl isopropyl 183*6 


one meta 
one meta 


1:2:5 dimethyl ethyl 
1:2:4 dimethyl ethyl 


184*8 

181*6 


- i*6 x 2 one ortho and one meta 


The formulae are thus 



m methyl ethyl. m methyl isopropyl. 1:2:4 dimethyl ethyl. 

There are exceptions to this, but the volumes are in all cases 
normal. 


V*. A. 

p methyl propyl 184*8 

m methyl propyl 184*1 ” ° ^ 

1:3:5 dimethyl ethyl 184*8 (1) 

1:3:5 dimethyl ethyl 183*9 (2) °’ 9 

This, so far as we can see, can only be explained by placing 
one group in opposition to the others. 



m methyl propyl. 1:3:5 dimethyl ethyl 

benzene. 

We assume that the opposed varieties of the different com¬ 
pounds would have normal volumes because the interaction of 
groups is impossible. 


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HYDROCARBONS AT THE BOILING-POINT. 


43 


All this seems to agree with our explanation of the two 
values for o xylene. 


CH* 

<7 

ch 3 

Vm 140*2 (Schiff) 
140*6 



Complex Aromatic Rings. 
(a) Condensed. 


The benzene nucleus is the only one of the type, which con¬ 
tains a single ring, for which data are available. The following 
is a series of such hydrocarbons. See Le Bas (loc. cit.) and 
ref. 


A ' H 

chJi 


\ 

(1) 


CH 



XH—CH 

CH—i 

CH=CH 

/ 


/ 

1 1 

CH, 


CH 

CH*CH 

\ 




CH—CH 

CH— 

(2) 

(3) 


(4) 


\ 


CH 


✓ 


Derivatives of all the above hydrocarbons are known except 
(1), but, as before stated, only (4) has been prepared. 

We now proceed to study a series of more complex hydro¬ 
carbons, which are wholly or in part of the type just mentioned. 
The series is made more complete by the use of the formula 
described in the appendix (q.v.). 



\ /\/ 
CH CH* 


Hydrindene. C 9 H ]0 
dm 0*957 b.p. 176° C =5 0*46 
V m . 144*0 (by formula) 
2 nVa. 170*2 (46 x 3*7) 

A for ring structure = -26*2 


One six-membered ring -15*0 

One five-membered ring -12*0 (vide ante) 


Total contraction = - 27*0 


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44 


LIQUID CHEMICAL COMPOUNDS . 


CH CH 

s \/ % 

CH C CH 

in c 1 <S:h 

\ /\ ^ 

CH CH 


Naphthalene Ci 0 H 8 . 


V« 1472 

177*6 (48 x 3*7) 


A for ring structure = - 30*4 


Since the contraction for a single six-membered ring is 
- 15-0, the contraction for two such rings is - 30*0. A con¬ 
traction of this magnitude is seen to apply to naphthalene, a 
compound containing a condensed ring system, which is evidently 
equivalent to two separate six-membered rings. 


CH ch 2 

s \/ \ 






CH 2 

Ah, 


\ /\ / 

CH CH, 


Naphthyl hydride C^H^. 


Vm 171*2 

2»Va 200*0 (54 x 3*7) 


A for ring = - 28*8 


If we compare naphthyl hydride with naphthalene, we get the 
following results:— 


[C 10 H 14 ] *=* 171*2 
[C 10 H 8 ] - 147*2 

A for 6[H] = 24*0 


Again, comparing toluene and hexahydrotoluene, we find— 

[C 7 H 14 ] - 141*8 
[C 7 H 8 ] = 118*3 

A for 6 [H] = 23*5 

It is thus seen, that, on reducing a substituted ring of the benzene 
extra hydrogen atoms possess volumes which are nearer 4*0 than 
to 37. 

The result is, that the apparent contraction for such a re¬ 
duced ring, is less than the normal, i.e., by an account equal 
to 6 (4*0 - 37) = 1 '8. Thus the contraction for the nucleus really 
is - 28*8 - i*8 = - 30*6. For naphthalene - 30*4. 


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45 


HYDROCARBONS AT THE BOILING-POINT 


Acenaphtenc C ]2 H 10 . 


CH 


CH 


0 1 

L 

\ 


\/ 

c 


\ 


c 
/ 

c 


CH 




-CH„ 


m.p. 103°, b.p. 277 0 d m.p. 1*03. 
By formula db.p. 0*903 if c = 0*46. 

V m = I 70*5 
5 w V a = 214*6 


A for ring = - 44* 1 


Two six-membered rings 2 x 15 - 30*0 

One five-membcred rings - 12*0 


Total contraction =* - 42*0 


Anthracene C 14 H 10 . 


CH 


CH CH 


c4 

i„ 

\ 


\/ 

- c 


CH 


C 

/\ 


\/ 

C 


V 


CH 


CH 


C C 

/\ ✓ 

CH 


H 


V» 195*5 

2 n Va 244*2 


A for ring = “ 48*7 


Two six-membered rings - 3 °‘° 

Two four-membered rings - 17*0 (2 x 8*5) 


Total contraction - 47*0 


Three six-membered rings would show a contraction of 
3 x - 15-0 = - 45 0, from which it follows that the above 
formula is the correct one. 


Phenanthrene C 14 H 10 


CH=CH CH=CH 

/ \ / \ 

(1) CH C-C 

\ S \ 

CH—C C 

\ / 

CH=CH 


s 

-CH 


CH=CH 

/ \ 

CH (2) CH 

\„- 


/ 

-C— 


CH=CH 

/ \ 


=C 

\ 

—c- 


\ / 

CH=CH 


CH 
CH 


Vw 196*0 
2»Va 244*2 

A = - 48*2 


The contraction for phenanthrene is similar to that for anthra¬ 
cene. It is thus probable that they have similar structure. If 
this were the case) phenanthrene would have a formula similar to 
(2) and not like that of (i). 


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46 LIQUID CHEMICAL COMPOUNDS. 

This structure would occasion a contraction of - 48*0. 

Two single six-membered rings 2 x 15 = - 30*0 
Two four-membered rings 2 x 8*5 = - 17*0 

A = - 47*0 

The first formula would show a contraction equal to 3 six- 
membered rings 3 x -15 0= - 45*0 

(b) Separated Rings. 

No data are available for compounds of this type, but with 
the help of the formula, we may find out how these rings affect 
the volume. 


Diphenyl C ia H 10 . 

b.p. 254 0 d^ 0-9961 

C = 0*46 Vm 180-0 

2 C 6 H 6 192-0 2 x 96-0 
less 2 H 6-4 

185-6 

V w =i8o-o (by formula) 

A = - 5*6 

There is reason to suppose that there is a special constitutive 
effect associated with the presence of two conjugated unsaturated 
rings. Accurate data, however, are alone capable of showing 
this definitely. 


m.p. 


7°'5 


& 


CH CH 

/ \ 

CH CH 

I II II I 

CH CH CH CH 

\ / \ / 
c-c 


The Polymethylenes C n H sn . 

The aromatic compounds, when reduced, give a series of 
saturated compounds called the polymethylenes. They are 
isomeric with the open-chain olefins, and are distinguished from 
them by the possession of ring structure. Only two or three 
compounds of this character have been directly investigated, viz. 
diamylene C 10 H 20 , hexamethylene QH 12 and its homologues 
hexahydrotoluene C 6 H U (CH 8 ), hexahydroxylene C 8 H 10 (CH 8 ) 2 . 

The values obtained for the others must consequently be calcu¬ 
lated values. C = 0*46, which is a number usually employed 
when unsubstituted ring compounds are dealt with. 


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HYDROCARBONS AT THE BOILING-POINT 


47 


TABLE XXI.— The Polymethylenes. 


Olefins. 

Vm. 

A for Ring. 

Vm. 

Polymethylenes. 

Propylene CsH 6 
Butylene C 4 H 8 
Pentylene C 5 H 10 
Hexylene CgH^ 
Heptylene C 7 H 14 
Octylene C 8 Hj 6 

66*6 

88*8 

110*0 

132*5 

154*8 

177*6 

-6*4 
-8*8 
- 12*0 
- 16*0 
-20*8 
! - 26*4 

60*2 

8o*o 

98*0 

116*5 

i34*o 

151*2 

Trimethylene (CH 2 ) S 
Tetramethylene (CH 2 ) 4 
Pentamethylene (CH a i s 
ft examethylene (CH a L 
Heptamethylene (CH a ) 7 
Octomethylene (CH 2 ) 8 


The diagram on next page shows how the contraction for ring 
structure varies with the size of the ring. 

Confirmative evidence in favour of the above contractions for 
single-ring structure is found in the following table. Since it is 
derived from the consideration of derivatives of the simple hydro¬ 
carbons, details concerning the derivation of 2«V a must be looked 
for elsewhere. 


TABLE XXII.— The Magnitudes op the Contractions due to Ring 

Structure. 


For For 

Polymethylenes. Vm. ring ring Vm. 

structure, structure. 


60*2 - 6*4 


Trimethylene— 
CH 2 

L> ch ' 


Tetramethylene— 

CH a — ch 2 

I I 8o*o -8*8 

CH 2 —CH 2 

Pentamethylene— 

CH a —CH a 


!h„—CH. 


\ 

/ 


CH 2 98*0 -12*0 


H examethylene— 


^ch 2 -ch 2 ^ 


ch 2 

V 


CH 2 116*5 -i6*o 




- 5*2 


■8-5 


12*4 


-15*0 


Other compounds. 
Epichlorohydrin 


1 87*5 _a 

92-2 2»Va | \ Q 

ch/^ 

Vfn. Diamylene. 

2117 C 3 H 7 —CH—CH a 

k 220*2 juVd d/Hj—i/H—C 8 H 7 

Vm. Thiophene. 

CH=CH 

849 , \_ 


97*3 2#V* c H=CH / 


Vm. 

96*0 


Benzene. 
CH—CH 


CH 

iii*o 2 n Va \ 

w—* 


CH 
CH—CH/ 


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48 


LIQUID CHEMICAL COMPOUNDS. 


It cannot be doubted, on the one hand, that the above-men¬ 
tioned contractions are the true ones, if we allow for the possi- 



Numbers of Members in Ring. 

Fig. 2. 

bility of a slight variation one way or the other, and on the 
other hand, that the volumes calculated for the polymethylenes 
are approximately correct 


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HYDROCARBONS AT THE BOILING-POINT. 


49 


The most interesting fact connected with these results is the 
one already noticed at the commencement of this chapter, viz. 
that the contraction for ring structure varies with the size of the 
ring . This is the result which we should expect, if the contrac¬ 
tion is additive in nature, that is, made up from the sum of small 
deviations of the individual atomic volumes from the normal. It 
is, however, remarkable, that those attempts which have been 
made, to elucidate this question, by means of other physical 
properties which show a marked effect for ring structure, give 
results which are opposed to the conclusions arrived at here. 
The view taken by Sir Wm. Perkin, in his study of molecular 
magnetic rotations, 27 is, that the magnitude of the constitutive 
effect is constant , and thus not related to the size of the ring. 
Independently of the question of the probable correctness of 
this latter view, a study of the question has led us to conclude 
that it is probably based on a wrong reading of the data. It 
is remarkable that Perkin at first calculated results which 
favoured the view, that the magnitude of the effect due to ring- 
formation varies with the size of the ring; but because these 
results appeared to him to be anomalous, he discarded this method 
of calculation for another one which seemed more satisfactory. 


TABLE XXIII. —Comparison of two Methods of Calculating the Effects 
of Ring formation on the Molecular Magnetic Rotations of Organic 
Compounds. 


No. of 
Members 
in Ring. 

Substance. 

M 

For Ring 
Structure. 

For Ring 
Structure. 

M. 

Substance. 


f Butyric Acid 

4‘47 2 



4-740 

Formic Acid + 3CH 2 . 

3 

-[ Trimethylene . } 


-0*331 

-0*599 


f Trimethylene. 


[ Carboxylic Acid j 

4-141 



4141 

{ Carboxylic Acid. 


f Valerianic Acid. 

5*513 



5*594 

Acetic Acid + 3 CH S . 

4 

-J Tetramethylene \ 


-0-465 

-0-546 


/ Tetramethylene. 


[ Carboxylic Acid j 

5-048 



5-048 

1 Carboxylic Acid. 


f Hexylic Acid . 

6-530 



6-531 

Propionic Acid + 3CH 2 . 

5 

-j Pentamethylene \ 


-0-639 

- 0*640 


/ Pentamethylene. 


\ Carboxylic Acid J 

5-891 



5-891 

i Carboxylic Acid. 


f n Hexane . 

6-646 



8-582 

Valerianic + 3CH 2 . 

6 

\ \ 


-0*982 

-0*607 


j Methyl Hexamethylene. 


l Cyclohexane . j 

5-664 



7*975 

1 Carboxylic Acid. 


4 


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5o 


LIQUID CHEMICAL COMPOUNDS. 


The magnitude of the effects for ring formation on the left- 
hand side of the above table, favour the conclusion arrived at 
from a study of molecular volumes, whilst those on the left-hand 
side, which were adopted by Perkin, give a different result 

It is not difficult to show, by making a summation of the 
atomic values, or by means of a calculation of the series-differ¬ 
ences S, that formic and acetic acids are anomalous, and not 
only these, but acetone and other compounds employed by 
Perkin in calculating his results. The average value of S the 
Series constant for the acids is 0*393, i.e. for O a . 


TABLE XXIV.— Acids. 


Substance. 

M. 

A. 

S. 

'Zntn. 

Difference. 

Formic Acid 

Acetic „ 

Propionic „ 

Butyric ,, 
Pelargonic ,, 

1-671 

2*525 

3- 462 

4- 472 
9590 

0-854 

0*937 

i-oio 

5 x 1-023 

(0-648) 

(o* 479 ) 

o *393 

0-380 

0-383 

1- 410 

2- 419 

3- 462 

4- 485 
9*600 

- 0*261 

- o*i 06 
± 0 

+ 0-013 
+ 0*010 



The Ketones. 



Acetone. 

Methyl Propyll 
Ketone / * 

3-514 

5-499 

2 x 0*992 

(o- 445 ) 

0-384 

3*444 | 

5-508 

- 0-091 

+ 0-009 


These first and second members of the respective series are 
not strictly analogous to the succeeding members as regards 
their molecular magnetic rotations, any more than they are for 
other physical properties, and thus they cannot be used to 
calculate the effects due to ring-formation. The values of M are 
relatively high for formic, acetic acid, etc., so that the calculated 
effects, due to ring structure, are thereby increased. This result 
makes it appear that the effect is independent of the size of the 
ring, a conclusion which is seen to be incorrect 

Perkin argued that because tri methylene carboxylic acid 
is the first member of the series, it should possess an augmented 
value similar to formic acid. This is not necessarily the case, 
because the former compound is differently constituted, since it 
contains a ring, and in any case, the amount of the augmentation 
differs considerably, even for different open chain compounds. 
Trimethylene carboxylic acid is sufficiently complex to exclude 


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HYDROCARBONS AT THE BOILING-POINT. 


5i 

the idea of such an augmentation, and it is of nearly the same 
complexity as butyric acid, with which it may suitably be com¬ 
pared. We believe that the position of a compound in a series 
has no significance, apart from complexity. 

It must also be observed that magnetic rotary power is a 
physical property which is much more sensitive to constitutive 
influences than molecular volumes, so that even slight changes in 
structure might considerably affect the values. An apparent 
difference in the observed and calculated results, and which is 
relied upon to indicate the extent of some constitutive influence, 
may consequently be the algebraical sum of several effects. This 
would vitiate to some extent the calculated effects due to ring 
structure determined by this property, and probably does so. 

In molecular volumes , on the other hand, we choose data 
which are only affected by the constitutive influence in question 
—ring structure, the others being negligible by comparison. 

Moreover, the corrections for this structure are very con¬ 
siderable. 

No physical property is probably so well adapted to the elucida¬ 
tion of the ring structure of chemical compounds as that of 
molecular volumes . 


The Naphtenes . 


These subjects are specially interesting, chiefly owing to the 
fact that they occur in many mineral oils and other natural pro¬ 
ducts. They do not, however, differ in character from the com¬ 
pounds of the preceding group. The data have been taken 
chiefly from Richter’s Organ . Chem . (Smith). Eng. edit. vol. ii.> 
p. 292. 


Hexahydrotoluene C 7 H 14 (Heptanaphtene). 


CH a 


/ 

CH, 

Ah, 




CH, 


CH—CH. 


\ CH / 


Vf« = 141*8 (Lossen and Zander). 

[C 6 H 5 ] = 92*8 
6[H] = 24*0 

[CH3] = 2 SS 

%Na = I42‘3 


For ring formation. Hexahydrotoluene C 7 H 14 141*8 
Heptylene „ 154*8 


A for ring = -13*0 

4 * 


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52 


LIQUID CHEMICAL COMPOUNDS, 


This value does not represent the real contraction for ring 
structure, since in these compounds the six extra hydrogens 
take up larger volumes (■ v.a .) than is usual with ring compounds. 


p Hexahydroxylene C 8 H 16 . 


CH—CH S 

/ \ 

CH, CH, 

Vm = 165*0 (L. and Z.). 

[C 6 HJ = 89*6 
2CCH3] = 51*0 

1 1 

CH, CH, 

6[H] = 24*0 


— 

N CH-ch 3 

5»Va = 164*6 


For ring formation. Hexahydroxylene C 8 H 16 165*0 
Octylene „ 177*6 


A 


-124 


Hexahydro m xylene C 8 H 16 (octonaphtene). 

The value of C for the preceding compound is C = 0*506. 

CH--CHj, 

/ \ b.p. 118 0 dn 0*7814 

CH, CH, 

| | db.p. 0*6782 Vm 165*1 by formula 

CH a CH—CH* 

\ / 2«Va 164*6 

XH, 

According to theory, there should be little difference between 
the volumes of this compound and that of the preceding one. 
This is found to be the case. 


Hexahydrocumene C 9 H 18 . 


CH 3 

/ 


CH—CH 

/ \ \ 


CH, CH, CH, 
CH, ^H, 


\ / 


CH, 


b.p. 148° djo 0*7870 

C = 0*506 + 0*031 = 0*537 
d b.p. 0*6766 V« = 186*2 

[C 6 HJ = 92*8 

= 70-0 (19 x 37) 
= 24*0 


2»Va = 186*8 
Vm — 186*2 


[C s H 7 ] 

[6H] 


Or from cymene. 

Cymene C 6 H 4 (CH 8 ) (C 3 H 7 ) 184*5 

less CH S - 25*5 


159*0 

plus H 3*2 
162*2 

Six extra hydrogen atoms 24*0 

2»Va = 186*2 
V w = 186*2 


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HYDROCARBONS AT THE BOILING-POINT . 

Hexahydropseudocumene C 9 H 18 (Nononaphtene). 

b.p. 135 0 d ia 07812 (Konowaloff). 


CH —CH S 

C 

o *537 

/ \ 



CH, CH—CH, 

1 t 

d b.p. 

0*6738 

CH 2 CH a 

v,« 

187*0 

\ / 



CH CH a 

Mesitylene C 9 H 15I 

162*8 


6H 

24*0 



186*8 


Vm 

187*0 


53 


It is necessary to note that although the compound contains 
two CH 3 groups in the ortho position, an arrangement which is 
generally accompanied by a contraction of about - 2*5, this does 
not appear from a consideration of the calculated volumes. 

It might be explained by assuming that the particular 
specimen examined was a compound with thetrans or “ opposed ” 
configuration. 


11 


ch 3 



CH3 CH3 

Opposed ” Hexahydropseudocumene. 


We do not, however, wish to lay much stress on this con¬ 
clusion, since the value is one which has not been found experi¬ 
mentally. The volume of the adjacent form would be 


186*5 - 2*5 = 184*0. 


QH3 



ch 3 


** Adjacent * ’ Hexahydropseudocumene. 


A General Study of the Terpenes. 

The data have been taken from Die Atherische Ole, 
Semmler, vol. i., 1906. 


(a) The Hemi-terpenes C 6 H 8 . 


^C-CH = CH S 
CHj/ 


Isoprene. 

V« 103*9 (Buff). 
2»Va 103*6 (28 x 37). 


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54 


LIQUID CHEMICAL COMPOUNDS. 


Isoprene is an open-chain diolefin. The volume of valerylene 

C 6 H 8 is 104 2. 

(b) The Olefin Terpenes (C 5 H 8 ) 2 . 

This is a little understood class of compounds. They are 
probably due to the polymerization of two molecules of one or 
other of the hemi-terpenes, at least in theory. 

The difficulty in calculating the values of these compounds is 
to know what value for C applies to them. 

From di-isoamyl iCjqH^ d^g 07358 b.p. 159*4 (Schiff). 
db.p. 0*6126. 

By calculation we find a value of 0 58 for C. This gives 
numbers which are about 5 o units lower than those calculated 
by the method of summation. 

Their theoretical volumes are:— 

C 10 H M (diisoamyl 232 
less 6 H - 23 

= 209 or 207*8 by the usual method. 


TABLE XXV.— The Volumes of the Olefin Terpenes. 


(Calculated by Formula.) 


Compound C 10 H 16 . 

b.p. 

d /. 

Vm by 
Formula 

2»V*. 

A. 

Myrcene 

172*0 

0*803IjQ. 

203*0 

207*8 

-4-8 

Alloocimene . 

188*0 

0-8172*,. 

202*4 

»« 

~ 5*4 

Anhydrogeraniol 

172*6 

0-8232,*., 

198*3 

»» 

- 9*5 

Linaloolene C J0 H 18 

165*8 

0-7882*, 

208 *9 

214*6 

- 57 


It is difficult to completely account for these numbers by 
means of the ordinary open-chain formulae. Since the values are 
calculated, it follows that we must wait for directly determined 
data before we can draw certain conclusions. 

On the other hand, the nature and origin of the compounds 
by no means excludes, in some cases at any rate, ring structure. 

Take, for instance, myrcene. 

The ordinary formula requires little modification to produce 
the following:— 


CH 8 

\C : CH . CH 2 . CH a —C—CH 

CH »/ ji 1 

CHjCHj 


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HYDROCARBONS AT THE BOILING-POINT 


55 


This would cause a contraction of about - 3*o. 
From this there is an easy transition to 


CH,^ 

CH S / 


C : CH . CHj|. CH a . C=CH 

I I 

CHjt-CHj 


which would cause a contraction of - 6*o. 

If we study the formation of the compounds by the dehydra¬ 
tion of certain alcohols, we also see the possibility of ring struc¬ 
ture. 


CH3 > 

ch y 


: CH. 


Geraniol ClflHiaO. 


CH 2 . CHj. C (CHj) : CH. CH 2 OH 


Triolefin (C I 0 H 1B ). Ring compound (C 10 H 16 ). 

CH». 

>C : CH . CH, . CH. . C(CH,) : C : CH. 

CH,/ 


CHj\ 

\c 

CH,/ 


Anhydrogeraniol 


: CH . CH . CH—C(CH.) 

U 


Both of the above compounds are possible, according as the 
neighbouring or the fourth hydrocarbon group provides the 
hydrogen atom which unites with the hydroxyl group to form 
water. 

I Linalool C l 0 H 18 O. 

ch 3 . 

\C : CH . CHj . CH, . C(CH 3 ) OH . CH : CH,. 

CH 3 / 

Triolefin (C 10 H !6 ). 

CH,. 

ch ^>C : CH . CH, . CH, . C(CH 3 ) : C : CH, 

Ring Compound (C 10 H 16 ). 

CH 3\ 

)C : CH . CH,. CH, . C(CH 3 )—CH 

ch 3 / 9 \V 

CH 

The above triolefin is similar to the preceding one—that is 
a similar dehydration of geraniol and linalool produces anhy¬ 
drogeraniol, if the open-chain formula properly describes it 

Linaloolene has two hydrogen atoms more than the com¬ 
pounds of formula C^H^. 

We think that it will be found that myrcene, alloocimene and 
linaloolene are the ordinary open-chain triolefins, but that an¬ 
hydrogeraniol, or the compound which is called such, is in reality 


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56 


LIQUID CHEMICAL COMPOUNDS . 


CH,v 

>C : CH . CH a . CH — C (CH,) 

CH,/ I || 

CH a —CH 

With this conclusion the contraction found in the table is in 
agreement 

Moreover, the molecular refraction of anhydrogeraniol differs 
from that of myrcene. 


Myrcene. Anhydrogeraniol. 

d l6 0*8025 /ad 1*4673 rfao 0*8232 /ad 1*4835 

M * 46*9 M = 47*2 

The values of A for myrcene allocimene and linalloolene 
can, at least in part, be thus explained. 

(a) The group 


ch 3 \ 

)C = CH - 
CH,/ 

is responsible for a contraction of — 2 *4 as in amylene. 

( b ) The second iso group might cause a contraction of 09 
as in compounds of complexity C 8 . 

Thus a - - 2*4 - o*9 - - 3*2 

1 nUS 2nVa - 207 8 - 3 2 = 204*6 


which is not very different from 203*0, which might be in error 
by a unit or so. 


(V) The Menthan or Terpan Terpenes (CgHg^. 

These compounds, which occur in many essential oils, are 
probably formed by the polymerization of isoprene or some other 
hemiterpene, with the formation of a ring. Thus:— 


CH 2 CH a C^ CH,. X CH^-CR, 

C—CH C—CH, -*■ C—CH C— CH, 

CH,^ CH,=CH ^ CH,^ ^CH,—CH ^ 

Two molecules of isoprene. Carvene. 

The volume of carvene is 190*3 (Schiff). 


The observed value for cymene V*» 184*6 

5nVa 184*8 


Cymene 
less 2 [H] 


Adft] 




184*6 

- 7*4 for unsaturation 

- of C,H 5 group. 

177*2 

12*8 if the four nuclear H atoms 

- are similar to those of benzene. 

190 o for carvene, 


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HYDROCARBONS AT THE BOILING-POINT 


57 


If, on the other hand, the four hydrogen atoms are similar 
to those in hexahydrotoluene [H] = 4*0, then the volume would 
be 193'2, which is about 3 units too large. 

The four extra hydrogen atoms are thus equivalent to four 
hydrogen atoms in benzene. 

The calculation verifies the formula for carvene. 


CH a CH a —CH a 

\ / \ 

C—CH C—CH 3 

/ \ ^ 

CH 3 CH a —CH 


We may now study the two phellandrenes. 
CH 3 ch 3 CH 3 ch 3 


\ / 


CH 


\ / 


CH 



i„ 

/ \ 

/ \ 

CH a CH a Phellandrene. 

CH a CH | 

1 11 

1 « 

CH CH 

CH, CH 

\ / 

\ / 

C 

C 

1 

II 

CH S 

CH, 

a Phellandrene b.p. 170® C. 

d 15-5 0-846 

& »» »» »! 

0*848 


By formula : a form, 190*2 ; $ form, 189*7. 


Phellandrene. 


C = 0*523 


Calculating the volume of the a form by summation, we find 


[C 10 H 14 ] = 184-6 
2[H] = 6*4 

2 nVa = 191*0 for a phellandrene. 

It has been shown that the hydrogen atoms in the nucleus, or 
those which partially reduce it, may 

(a) resemble those of benzene, H = 3*2 V« 190*3 

(b) „ „ hexahydrotoluene H = 4*0 Vm 193*0. 

Carvene has been shown to answer to the first condition, and 
apparently a phellandrene also. 

Limonene and dipentene on the other hand answer to the 
second condition. 

Limonene b.p. 177*8 d, 5 . 5 0*848 C = *523 V m 193*1 


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58 


LIQUID CHEMICAL COMPOUNDS. 


TABLE XXVI.— The Calculated Volumes op the Terpenes. 


Terpenes C^H^. 

b.p. 

d 16 - 5 * 

db.p. 

V w (calc.). 

/*• 

f Limonene 
y Dipentene 

Carvene 

Sylvestrene . 

- a Phellandrene 

0 

Terpinene 

i 77 °-i 78 

178 

175 

176 

170° 

170° 

180 0 

0*848 

0*848 

0-853*) 

0-85115-5 

C846 

0*848 

O-849 

0-7043 

0-7043 

07159 

07165 

0-7150 

0-7169 

0*7134 

i 93 *i 

i 93 *i 

190-0 

189*8 

190*2 

189-7 

190*6 

1-4746 

1-4740 

by obs. 190-3 
i *4747 
i *4732 
i *4759 
1*4846 


Whether these distinctions are valid or not, remains at present 
uncertain, but in any case the various menthan terpenes possess a 
range of volume of only 1897 - 190*6 or at most 1897 - I 93 'i. 

This of course indicates that their structures are so little 
different, that the molecular volumes are not very much affected 
by such differences as do occur. These are mostly indicated by 
the positions of the two ethenoid linkages. 

One or two other terpenes of a somewhat different type re¬ 
main to be noticed. 

Thujen b.p. 151 d 15 . 8 0-851. 

If C as 0*523 d b.p. 0-7281 V m = 186-5. 

The volume of this compound is considerably smaller than 
the terpenes just enumerated. 

The formulae which have been ascribed to a and ft tanacetene 
are:— 


a Tanacetene. 
CH3 CHs 

OH 


CH* 



Tanacetene. 
CH3^ ^OH3 

CH 



CH OH 

\/ 


cb 3 


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HYDROCARBONS AT THE BOILING-POINT 


59 


By summation, we find 

Ci 0 H |4 199*8 (54 X 37) 

2H 6*4 

'ZnVa = 206*2 
Vm = 186*5 (by formula) 

A = - 197 for ring. 

This contraction is somewhat larger than for a single six- 
membered ring, viz. - 15*0. 

Two four-membered rings 2 x - 8*5 = - 17*0 

One three and one five-membered ring - 6*3 - 12*0 = - 18*3. 

The observed contraction is nearer the latter than the former. 
In any case it is not compatible with the idea of a single six- 
membered ring, so that tanacetene must be considered to be 
possessed of a bi-cyclic ring. 

A further investigation of bi-cyclic compounds of this type is 
not desirable at present, since the value C = 0*523 which has 
been applied to ordinary terpenes may not be quite true for 
these, and we have no means of ascertaining the true value. 
Direct data for one such compound would furnish the neces¬ 
sary material for such an investigation, but it is at present 
wanting. 

One point of interest exists, which is, that the contraction for 
a single six-membered ring does not differ much from those 
marked by what we may call cross-linking . This term is used 
to distinguish these from bridged rings . Thus we may men¬ 
tion :— 


n a = - 16*o 

(H+4 A = 2 x - 8*5 = - 17*0 

riHy + r A = 6*5 + 12*1- 18*5 

The small difference between the contractions for the two 
classes of compounds makes it difficult to distinguish between 
them, since a slight difference of this magnitude might be due to 
small additional constitutive effects. 

The following is a list of the reduction products of cymene :— 


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6o 


LIQUID CHEMICAL COMPOUNDS. 


TABLE XXVII. 


Compound. 

Vm. 

Apparent 
effect of ring 
formation. 

3 »V«. 

C. 

Cymene C 10 H 14 

184-6 

- 15*0 

184*8 

0*523 

Carvene C 10 H 16 

190-3 

- 169 

190*3 

»» 

Menthene C 10 H 18 

[i 9 8-8] 

- 15*8 

197*4 

»» 

Hexahydrocymene C^H^ 

[808-3] 

- 13*0 

208*6 

»» 


The six extra hydrogen atoms in the fully-saturated com¬ 
pound hexahydrocymene possess volumes of [H] = 4*0. 

The hydrogen atoms in the nucleus of all the other com¬ 
pounds have been regarded as similar in volume to those of 
benzene [H] = 3*2. 

(c) Catnphane Terpenes C 10 H 16 . 

These terpenes belong to a second class of ring compounds 
which are distinguished by the possession of bridged rings. None 
of these have had their molecular volumes directly determined 
except pinene, but two derivatives— camphor C 10 H u O and 
borneol C 10 H 180 —have been determined by Kehrmann 28 . These 
data are sufficient to enable us to ascertain the nature of the 
rings which are characteristic of this class of compound. 


Camphor. 

CH 2 - CH -CH 2 


CH3-C-CH3 


CH 2 -C-C:0 

1 

CH3 

V« 188-6. 

We find by summation— 

CujHw 56 X 3-7 = 208*2 
: O ii*o 


2nV a 219*2 
Vm 188*6 


A = - 30*6 


Borneol. 

CH 2 -CH-CH 2 


CH3-C-CH3 


CH 2 - C-CH (OH) 

I 

CH3— 
v m 190*5. 

C 10 H 18 58 x 3*7 = 214*6 
•O. T4 

2nVa 222*0 

Vm 190*5 


A= - 31-5 


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HYDROCARBONS AT THE BOILING-POINT 


61 


The ring structure of these compounds is thus found to give 
rise to a contraction of about - 30, which is double that for a 
single six-membered ring. 

In consequence of the absence of data we shall be under the 
necessity of calculating the molecular volumes by means of the 
formula. The value of C is doubtless 0*460, since this value has 
been found to be appropriate for a large number of ring com¬ 
pounds which do not possess side chains of more than one car¬ 
bon or equivalent atom. 

Camphene C 10 H 16 m.p. 48° b.p. 160° 
d^ 0*8481 0 = 0*46 

d b.p. 0*7578 V m = 179*5 
Ci 0 H 16 207*2 
V w 179*5 

A = -27*7 for ring. 

This difference represents the value of the contraction for 
ring structure, and is much larger than for a single six-membered 
ring. 

We thus conclude that the ring structure is similar to that 
which has been found for camphor and borneol. 


For two five-membered rings A = 2 x -12 = -24 
For two six-membered rings A = 2 x -15 = -30 

Camphene C 10 H 1(J may theoretically be supposed to be formed 
as follows:— 


CH S —CH—CH S 
CH a —ili—CH 3 
iH 2 — CH(CHJ— CH S 


CH a - 


-CH- 


-CHo 


CH, 

A 


Ah — ch 

II 

H 2 —CH(CH a )—CH 



Ah, 


Ah, 


By analogy with camphor and borneol, a compound with the 
above structure should possess a contraction of about - 30*0. 
The calculated value is about - 28*0. 

As before indicated, two five-membered rings produce a con¬ 
traction of - 24*0, which is a number considerably below - 30*0. 


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62 


LIQUID CHEMICAL COMPOUNDS . 


It is difficult to account for this, on the basis of the plane for¬ 
mula, but remembering the tetrahedral arrangement of the car¬ 
bon valencies, we may substitute the following one, which has 
also been proposed by O. M. Foster, 28 for bromnitro camphane 
and other compounds of this type. 



This formula shows the two halves of the camphor molecule 
forming an angle with each other like a partially opened book 
set on end. 

The carbon groups shown by the dotted line, together with 
the corresponding ones above, are in a position to influence one 
another so as to form a potential four-membered ring— 


CHj CH 2 

!h 2 .Jh(OH) 

The additional contraction for this, would have to be added 
to - 24*0, for the two five-membered rings, and so the observed 
contractions would be partly accounted for. 


Pinene C 10 H lfl . 


CH 2 —CH- 

/ \CH a 
CH — C- 


-CH, 


CH 


b.p. 156° d b.p. 07421 (Schiff). 49 * 
V w = 183*2 

. By formula— 

cLjo 0*858 C = 0*46 
d b.p. 07487 
Vtn 1817 
Since [C 10 H 16 ] = 207*2 


Contraction from observed value A = 207*2 - 183*2 = - 24*0 
Contraction from calculated value A = 207*2 - 181*7 = - 25*5 


* The compound with this density was called by Schiff terpene, but is probably 
pinene. 


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HYDROCARBONS AT THE BOILING-POINT . 63 

The theoretical contraction is on the basis of the plane 
formula:— 

One four-membered ring - 8*5 
One six-membered ring - 15*0 

There is also a difference between the contraction deduced 
from the data and that indicated by the summation method, as 
for camphene, but it is not so great. 

Fenchene C 10 

CH a -CH- C 

(CH,),<i 

ch,—-!;h—< 

Two five-membered rings A = — 354*0 
The difference in this case is (26*4 - 24) = - 2*4 

The result may be due to the grouping 

-C-™. 

- CH 

which in ft amylene shows a contraction of - 2*4. The idea is 
that the association of methyl groups and | = | gives rise to special 
contractions. 

It is probable that the grouping 

C 



which is found centrally, is responsible for a contraction of 
about - 1 ’0, as in tetramethyl methane 

CH 3 

ch 8 —i—CH« 

It is seen that camphor, borneol, and the parent hydrocarbons 
possess contractions which are very much greater than for single 
six-membered rings. In fact, bridged rings of some kind are 
denoted, since, as we have seen, the types of double rings dis¬ 
tinguished by cross-linking are not subject to very much larger 
contractions than for single six-membered rings. 



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6 4 


LIQUID CHEMICAL COMPOUNDS . 


(d) The Sesquiterpenes (C 6 Hg) 3 . 

We have noticed the following stages in the polymerization 
of isoprene C 6 H 8 . 

(i) Two molecules forming the menthan terpenes with a 
single ring. 

(ii) A bridging of the ring. 

A further stage is indicated by the union of three molecules 
of isoprene to form the sesquiterpenes. 

Although the compounds C 16 H 24 are all classed as sesquiter¬ 
penes, it by no means follows that they are all alike in structure. 
Indeed it is probable that many types of structure exist. 

In any case the value of C = 0 46 may still be employed for 
the ordinary type of sesquiterpene. 

The sesquiterpenes C 15 H 24 . 

Clovene b.p. 262 d 16 0*932 

Cedrene „ 261 „ 0*932 

Ledene „ 264 „ 0*935 

For clovene Vm'= 265-6, and a similar value for the others. 

By the summation method, 

[C 16 H 24 ] = 310*8 (84 X 3 * 7 ) 

Vm = 265*6 

A = ~ 45*2 (3 x - 15*0). 

Thus the condensation of three molecules of isoprene and 
the presence of three six-membered rings would account for the 
molecular volumes obtained. 

It is obvious that if the complex molecule consist of three 
molecules of isoprene, then it must include a bridged ring, that 
is, a ring which contains a central group linked to two of the 
peripheral carbon atoms. Otherwise only two six-membered 
rings would be possible. For our present purpose it is im¬ 
material which of the camphane terpenes forms the basis of the 
sesquiterpene molecule. We shall assume that it is camphene. 
Under these circumstances the formula would be 

CH a CH S 

I I 

CH a -CH-CH CH S -C CH*-CH-CH—CH 2 —C 

CH 3 l—CH 8 -> CH3J—CH3 

CH*-C-CH CH 3 -CH CH 2 -C-CH—CH 2 — OH 



camphene. isoprene. sesquiterpene. 


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HYDROCARBONS AT THE BOILING-POINT 


65 


The above molecule should possess a volume of 268 0, which 
approximately agrees with the number calculated. If the value 
- 2-4, just shown to be necessary, be deducted, we obtain the 
calculated value 

2»V a 268*0 - 2*4 = 265*6 

By formula 

Vm = 265*6 

Clovene terminates in an olefin linking, and this is capable 
of taking on another molecule of isoprene. 

Semmler in his Atherische Ole classes the following as 
tri-cyclic:— 


Aromadendrene 

b.p. 

260-5 

o*g 249 1# 

Clovene 


261-2 

o* 93 °i 8 

Cedrene 


261-2 

o* 9359 i 5 

Ledene 


264 

o *9349 

Vetiden 


255 

0*9332 


and doubtless there are others. 
Cadinene is described as 



/ \ / CH \ / \ 
CHg CH 3 CH a CHg 



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66 


LIQUID CHEMICAL COMPOUNDS. 


Such a compound as the last would have a volume of 

# 

Carvene C 10 H 16 190*5 
Isoprene C 5 H 8 103*9 


less for six-membered ring 


294*4 

~i5‘o 


Volume of cadinene 279*4 


(c) Diterpenes (C 5 H 8 ) 4 . 

Among the diterpenes we find 

Diterpene b.p. 320° d 16 0*9535 d* 0*9414 

Colophene 318-320° d 1B 0*940 

Still utilizing the value C = 0*46. 

d b.p. 0*7714 Vm 352*4 

we obtain the following results. 

By summation, 

[CioHaJ = 414*4 (112 x 3*7) 

V m = 352*4 


A = -62*0 (4 x - 15*5). 


A better method would be 


^10^90 4*4*4 

less for ring - 6o*o 


less for CH 8 | 


354*4 

-2*4 


%Na 352*0 
Vm 352*4 (by form.). 

A formula which would answer to the above description 
is the following:— 

ch 8 

-CH—CH,—i CH,= CH 


CH 




CH- 


CH-* 


H 9 


-CH—CH a —CH CH a =C 

£ 

ch 8 

CH,-C-CH—CH,— A —CH,-CH 


a' 

CH,- 

CH,— 


,-L. 


CH, 


Ah, 


-CH—CH,—CH—CH,—C 


Diterpene. 


^H, 


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HYDROCARBONS AT THE BOILING-POINT. 


67 


A molecule of this character should possess a volume of 
about 352*0, and, as it terminates in an olefin link, the poly¬ 
merization process could continue until compounds of the com¬ 
plexity of india-rubber might result. 


The Effect of Cross Linking. The Double Bond. 


It has been stated that compounds which show the cross- 
linking, as distinct from those which possess bridged rings, are 
marked by contractions very little different from those which are 
characteristic of single rings. 

The following are examples of this type of structure with the 
contractions appropriate to them :— 


// c \ 

0 / o 

c 

O G 


(I) 


(2) 


* - {:£) 

- = -18*0 

A a - 15*0 

.* = {:£} 

( 

- 

C 

c 

/ 

\ 

/ \ 

/l\ 

c 

C 

c c 

c c 

A 

1 

c 

A A 

if i 

\ 

./ 

\/ 

N/ 

( 4 ) 

(5) 

(6) 

*-{:!? 

1 = -17-0 

A =* -15*0 



_//°V 


N,/ 


/ c \ 
0 c 




It is also seen that ring (3) does not differ from ring (6) as 
regards contraction. 

The cross linking does not produce any marked effect 
additional to that produced by a single six-membered ring, 
provided that it does not include a C or other atom centrally 
situated . 

If it does include such an atom or groups a very marked in¬ 
fluence is exerted on the volume in addition to that produced 
by the former type of ring, due to an attractive effect of the 
central carbon atom on the peripheral atoms, ar\d th$ qorrespond- 
ing reacting effect on the central atoms. 

5 * 


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68 


LIQUID CHEMICAL COMPOUNDS, 


In the first case , that of simple cross linking, although it 
involves the existence of two rings, can scarcely be distinguished 
from a single ring of the same outline as the first. 

This is unfortunate from the point of view of chemical di¬ 
agnosis; but if we ascertain beforehand the number of olefin 
linkings present, by the method of molecular refractions, no 
difficulty will be experienced in giving the compound its true 
structure. 

The boiling-point is also distinctly lower than for a single 
ring terpene, 150° or so as against 170° - I76°C. 


The Olefin Link. 


It probably will be a matter for remark that the olefin link 
does not occasion any apparent contraction at the boiling-point. 
If we consider the curve showing the contractions for a series of 
ring compounds—the polymethylenes, for example, we shall 
find that on extrapolation from Diagram (2) p. 48, the olefin link 
would correspond to a considerable contraction. 

There is, however, found to be no contraction. This result 
calls for an explanation. 


v 


c 



/ c 

c 



Nc 




A + o 

or - 3*5 by extrapolation. 


A - 5*0 



A - 8*5. 


If we apply the same principle to the double bond as was 
brought out by cross-linked rings, we find an explanation of the 
zero value. 

The principle involved is as follows: (a) In simple cross 
linking the changed direction of the link probably does not 
by itself involve any change in the shape or structure of 
the molecule, and thus there is no great change in magnitude 
of the contraction. It is only when an atom or group are in¬ 
cluded, that a considerable modification takes place in the shape. 
Under these circumstances the magnitude of the contraction is 
greatly changed. 

( b ) In the olefin type of linking, or for that matter the acetylene 


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HYDROCARBONS AT THE BOILING-POINT 69 

type, no change in the structure is discernible from that char¬ 
acteristic of the saturated atom for the reason stated. 

- ch 2 - ch 2 - - ch = ch - -c = c - 

When, however, 

CH S - CH = CH, changes to ^CH, 

CH/ 

a modification in the constitution has occurred, which is at once 
noticed in the volume. 


In the ring system 



I H 


it is evident that structure I (J?) does not occasion any marked 
change in the shape or volume of the molecule, because the 
affinity is directed to the penultimate carbon atom, instead of to 
the neighbouring one. It is simply a case of change in the 
direction of the affinities. The shape and volume of the molecule 
are chiefly determined by the single linkings of the six-membered ring. 

In II, there is included a carbon or alkyl group, and this 
exercises a modifying influence on the volumes of the peripheral 
carbon atoms, and so on the molecule. 

In compounds with an olefin link the atoms are not more 
favourably situated to act on each other than in the saturated 
chain. No change in the volume occurs, that is, there is no 
special action due to unsaturation, at least under the circum¬ 
stances. 

In the trimethylene ring , as compared with an open-chain 
compound with an olefin link, the atoms are more favourably 
situated for interaction, owing to the greater concentration of 
matter, for the change in the direction of one of the carbon 
valencies, involves a change in the position of one of the methy¬ 
lene groups, relative to the others. 

Thus owing to the distortion of the original straight-chain 
molecule, there is a contraction in volume. 


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7 ° 


LIQUID CHEMICAL COMPOUNDS. 


This occurs 

when CH 8 ~CH 2 —CH 2 —CHa—CH 3 
changes to 


CH a \ 

CH S / 


CHj—CH a —CHj 


when 

CH S —CH a —CH 2 —CH a —CH a —CH 3 
changes to 

or when CH 3 —CH = CH a CH aX 

| >CH 2 . 

changes to CH a / 

In all these cases the affinity forces are more effective than in 
linear arrangement because of the greater concentration of matter. 

It is also for this reason that the structure which has been 
named partial ring structure involves very noticeable contrac¬ 
tions, although not so large as for completed rings. The curva¬ 
ture of the hydrocarbon chain results in diminished volumes, 
owing to the greater concentration of matter, as compared with 
what we call straight-chain compounds. 

These results are thus just what we should expect, if we 
assume that the carbon atoms or hydrocarbon elements of the 
molecule exert an action of affinity on each other, not only in 
the direction of the linkings but in other directions as well. The 
greater relative efficiency of the attractive forces makes it impos¬ 
sible for the expanding heat forces to be so effective, and so there 
are contractions. 

It would appear that the above facts can be included in a 
single generalization which may be stated in the following 
terms:— 

When any molecular change involves a change in its configur¬ 
ation! that is when one or more atoms are displaced relatively to 
the others , then there is a distinct effect on the molecular volume . 
When , however, the change includes simple displacement or a change 
in the direction of a linkage only , no marked effects on the molecular 
volume occur . 

Conversely , modifications of the molecular volumes of compounds, 
other than those due to simple changes in composition , may be 
referred to changes in the shape of the molecule . 


CH a 

/ \ 


ch 2 

ch 2 

(Ihj 

Jhj 


\h/ 


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HYDROCARBONS AT THE BOILING-POINT 


7 i 


This generalization apparently covers all, or nearly all of the 
constitutive effects which have been noted in connexion with 
carbon compounds and is doubtless of great importance. 

Ring Systems . 30 

Ring systems are divisible into the following classes:— 

(a) Simple ring systems. Example, Benzene. 

(&) Multiple ring systems. 

(i) Condensed—naphthalene. 

(ii) Separated rings—diphenyl. 

If n be the number of carbon atoms in the compound and 
N the number of atoms or groups in the ring, we are able to 
find the nature of the molecule by the amount of the contrac¬ 
tion per atom given in the following table:— 


TABLE XXVIII.— Contractions, etc., for Different Simple Rings. 



No. of atoms 
in ring. 

N 

^ . Contraction 

Contraction. ^ 

Three-membered 

3 

- 6-0 “2’0 

Four-membered . 

4 

- 8*5 - 2*12 

Five-membered . 

5 

-12*0 - 2*40 

Six-membered . 

a 

- i5’o - 250 

Seven-membered 

7 

- 20*8 - 2*97 

Eight-membered 

8 

-26*0 -3*25 


The last column is especially useful in distinguishing condensed 
from separated rings. 

In these, if the number of C atoms or others like O, S, N be 
n and the number of groups, as measured by the contractions be 
N, then N > = or < than n. 


{a) Condensed Rings. 

Example, naphthalene c 10 h 8 . 

In this case N - n = a positive number. 

The contraction is - 30*0. Dividing this by an average value 


of Tj = 2*50, we find that the number of groups by calculation or N 


30*0 

2*5 


12. 

N - n = 12 - 10 = 2, that is N ^ n by 2. 


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72 


LIQUID CHEMICAL COMPOUNDS. 


Since the number of carbon atoms in C^Hg or n is io*o, then we 
conclude that naphthalene contains a double-condensed ring system^ 
and that there are two atoms common to both rings. 

CH CH 


CH CH 

✓ \/ 

CH C* 

1 H 

CH C* 

\ /\ 

CH CH 


\h 

CH 


Naphthalene. 


s \/ x 

CH C* CH 

Ah c** Ah 

x /\ s 

c* c* 

l',H a -llH, 

Acenaphtene. 


In acenaphtene C 12 H 10 (condensed ring) the contraction is 
- 45 0, and a similar calculation can be made. 

— = 18 or N 

2*5 

N-n=i8-i2 = 6 


There are at least three rings in the compound. 

If we observe the diagram, we shall see that three carbon 
atoms are marked by * and one by **. This is to indicate that 
in the one case three carbon atoms are common to two rings, 
and in the other one carbon atom is common to three rings. 

This is somewhat more than a formal statement, because it 
indicates that the three common C atoms are subject to double 
the compression that the other or peripheral carbon atoms are, 
and in the other case the single carbon atom has thrice the 
compression. 

There is a fundamental principle at the back of these con¬ 
tractions, which is, that the mutual attractive influences exist, 
which result in diminished volumes. The result is, therefore, 
that if the contraction is contributed to by the action of one 
carbon atom on all the others, it, in a similar manner, is acted 
upon by the other atoms, and so the contraction is doubly 
affected. 

It is, however, to be observed that the C atom of one ring 
does not influence the carbon atom of another ring unless it 
forms part of this ring. 

The presence of side chains, of course, complicates matters, 
but in this instance 


n > N 

so that the formula for the compound can be fairly well made 
out. 


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HYDROCARBONS AT THE BOILING-POINT. 


73 


(b) Separated Rings. 

Example, diphenyl C 6 H 5 - C 6 H 6 
In this case N - ft = O 

A calculation similar to the above will indicate the nature of 
the ring system. 

The existence of other constitutive effects besides that of ring 
structure of course makes it more difficult to assign a formula. 


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CHAPTER III. 


THE MOLECULAR VOLUMES OF ORGANIC COMPOUNDS 
CONTAINING THE HALOGENS. 

The Halogens. 

KOPP calculated the volumes of chlorine, bromine, and iodine in 
the combined state as :— 

[Cl] - 22-8 [Br] - 27-8 [I] =* 37-5, 

which he showed were not very different from their free values. 

[Cl] = 227 [Br] - 26-8 [I] - [34-0] 

(Kopp) (Thorpe). (Billet). 

Those proposed in the present treatise are similar:— 

[Cl] = 22-1 [Br] = 27-0 [I] = 37*0. 

The halogens are all monovalent, and in this respect, as 
perhaps in others, they resemble hydrogen. 

Fluorine F. 

Compounds of the type R - F have not been investigated. 
Only one or two data for fluorine compounds exist altogether. 
They are:— 

CgH 0 F ioi*6 (Young) 

UgHg 92'8 

F = 8*8 

As F s 53*8 (Thorpe) 

As 27*8 

3 F = 26*0 

F = 8*7 

In order to confirm, if possible, the above value, a few com¬ 
pounds, indiscriminately chosen from chemical literature, have 
been studied by means of the formula. 

Before calculating the values, it will be necessary to know 
those values of C which are applicable to such compounds. 

74 


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ORGANIC COMPOUNDS CONTAINING THE HALOGENS . 75 

TABLE XXIX. 


Substance. 



d b.p. 


c. 

CH a : CH . CH,C 1 . 

do 

0*9610 

d« 

0*9002 

0*468 

CH,. C 0 C 1 .... 

tt 

1-1377 

d„ 

I*0570 

0*482 

CH a Br. CH,Br . 

tt 

2*3132 

dm 

1-9312 

0*450 


Mean value of C 

• 

0*467 


It should also be noticed that when atoms like F, Cl, Br and 
I occupy the a and ft positions in the hydrocarbon chain, there 
are contractions. These contractions have been shown to be due 
to a curved configuration of the hydrocarbon chain (vide prox). 
Thus:— 

CH 2 -CH 2 -X 

I N 
» 

; 

CH 2 -CH 2 -y J 

It will be shown that the above configuration is responsible 
for a contraction, the magnitude of which is dependent on the 
size of the partial or potential ring. A few such examples 
are:— 


TABLE XXX. 


Substance. 

Vtn. 

2»V a . 

A. 

CH Br : CH Br . 

91*4 

93-0 

- i*6 

CH a I . CH a Cl . 

101*3 

103-3 

-2*0 

Mean value 

. 

-1*8 


TABLE XXXI.— The Volume of Fluorine (by Calculation). 


Substance. 

b.p. 

d /. 

Vm. 

Sum. of 
at Vols. 

-i*8. 

F. 

CH F a . CH a I . 

89*5 

2*2412,, 

94*1 

65*9 

2 x 9*1 

CH F Br . CH 2 Br . 

121-5 

2 ‘ 2 6 33 io 

103*0 

95*9 




Mean for F 

. 

8*4 


Data due to F. Swartz. 31 


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76 


LIQUID CHEMICAL COMPOUNDS. 


If we consider the probable errors incident to this indirect 
method of calculation, we must conclude that the result is in 
good agreement with the former values. 

The value already obtained for fluorine, viz.:— 

[F] - 87 

is thus the correct one. 


Chlorine Cl. 

In considering homologous series such as those of the alkyl 
halogen compounds, it should be borne in mind that the atomic 
volumes, calculated by the usual method of differences, are liable 
to be affected by influences which are of a constitutive nature, 
and which really act on all the atoms of a molecule. It follows 
that the results obtained by this means are likely to be different 
from the true values. 

The errors to which this method of calculation is liable, are 
considerably diminished, if we take the average of a large number 
of results, but this really amounts to ignoring differences below a 
certain magnitude. 

There is an alternative method which is not based upon com¬ 
parisons at all, but which enables us to calculate the atomic volumes 
from a consideration of individual compounds. This method 
depends upon a principle found to hold in the hydrocarbon 
series, and which is, that the relative volumes of the atoms are 
maintained in any series of similarly constituted compounds. 
Thus the relation [C] = 4[H] is generally true. The principle 
in question is that of constant atomic volume ratios . 

It is possible that the ratios between the atomic volumes may 
not be quite the same as those assumed, but this error would not 
appreciably alter the form of the curves obtained. These conse¬ 
quently indicate the nature of the changes in the volumes of the 
atoms from compound to compound in a series. 

Hydrochloric acid HC 1 . 

By D. Bertholet’s formula, V = -^r = ** * ^ * . 

J D P k (2T k -T) 

Tk = 325 0 C P K = 86 atmos. T b.p. 238° C. 

Vm = 33 ’i. 

The volumes of the following compounds are considerably in 
excess of the normal. 


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ORGANIC COMPOUNDS CONTAINING THE HALOGENS . 77 

TABLE XXXII. 


Substance. 

V m . 

2 »Va. 

A. 

HC 1 . 

33 *i 

25*8 

+ 7*3 

CHg . Cl . 

50*4 

48*0 

+ 2*4 

C a H 6 Cl . . 

717 

70*1 

+ 1*6 


Such abnormally large volumes are characteristic of the 
initial members of most series. In these cases they may be due 
to the influence of the hydrocarbon and hydrogen elements, since 
the volumes of methane and ethane are considerably in excess of 
the volumes which we should expect them to have, from a com¬ 
parison with succeeding members of the paraffin series. 

In any case, it is probable that the volatile hydrogen is 
responsible for these augmentations. It will be borne in mind 
that the free and combined values of chlorine are similar. 

Free value* [Cl] = 227. Combined value [Cl] = 22*1. 


TABLE XXXIII.— The Alkyl Chlorides. 


Substance. 

Vm. 

Vols. of 
Hydrocarbon 
Groups. 

Cl. 

C 8 H 7 C 1 . 

91*7 

70 

217 

C^Cl . 

ii 3*5 

92*3 

21*2 

c 6 H n ci. . 

135*3 

114*1 

21*2 


Mean value [Cl] 

= 21*4 


It is probable that chlorine, like carbon, is an integral number 
of times larger than hydrogen. This is seen from the following— 

C 8 H 7 C 1 917 C 4 H 9 C 1 113*5 

C 8 H 6 C 1 84*4 CgHnCI 135*3 

2[H] = 7*3 [CHJ = 21*8 = 3 X 7*3 (approx.). 

Since [Cl] = 21*4 = 3 x 7*2 (approx.) 

It follows that [CHJ = [Cl] = 6[H]. 

This relation enables us to find the number of hydrogen 
equivalents W in a series, and so the volume V/W of such an 


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78 


LIQUID CHEMICAL COMPOUNDS, 


equivalent. These values show how the volume of the atom 
hydrogen varies in a particular series. 

TABLE XXXIV.— The Volumes of V/W in the Alkyl Chlorides. 


Substance. 

w. 

V w . 

V/W. 

HCl 

7 

33 ‘i 

4728 

C 3 H 6 C 1 . . 

19 

717 

3*774 

c 8 h 7 ci . . 

25 

917 

3*668 

C 4 H # C 1 

31 

ii 3*5 

3*661 

C 8 H u C 1 . . 

37 

135*3 

3*657 


The Unsymmetrical Polychlorides . 

The successive substitution of chlorine for hydrogen in 
methane (CH 4 ) or ethane (C 2 H 6 ) does not correspond to equiva¬ 
lent differences in the volumes or the boiling-points. 


TABLE XXXV. 


Substance. 

b.p. 

A b.p. 
for Cl-H 

Vm . 

A for 
Cl-H 

CH 4 . 

-164° 


380 




140 


124 

CH S C 1 .... 

- 24 ° 


50*4 




65-6 


M *7 

CHjCL, .... 

+ 41*6° 


651 




19*6 


19*4 

CHC 1 8 .... 

6l"2° 


84*5 




15*5 


19*2 

CC 1 4 . 

767° 


103-7 


ch 8 .ch 8 . 

- 93 ° 


567 




105-5 


15*0 

ch 8 .ch 9 ci 

4-12-5° 


717 




71*0 


17-2 

CHj.CHCJj . 

83 - 5 ° 


88-9 




iro 


19*1 

CH 8 .CC 1 8 

74 - 5 ° 


108-0 



We see that in both series there is a decrease in the boiling- 
point, and an increase in the volume for every substitution of 
chlorine for hydrogen. 

In the following table which shows the values of chlorine in 
the different compounds, we assume that the volumes of carbon 
and hydrogen are similar to their values in the hydrocarbons. 


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ORGANIC COMPOUNDS CONTAINING THE HALOGENS . 79 

TABLE XXXVI. —The Polychlorides. 


Substance. 

Vm. 

Volume of 
Hydrocarbon 
Group. 

n Cl. 

R-Cl .... 



21*5 (average) 

CHjCl, .... 

65*1 

22*1 

2 x 21*5 

CH Cl, 

84*5 

18*5 

3 X 22*0 

CC 1 4 . 

IO37 

14*8 

4 x 22*2 

CHj.CHCl a . . . 

88*9 

44*5 

2 x 22*2 

CH 8 .CC 1 8 

io8*o 

40*8 

3 x 22*4 


Since [Cl] = [CHJ 

[Cl] = } x [CH S CH C 1 J = } x 88*9 = 22*2. 

This value is similar to the one found in the table by another 
method. 

We conclude that the average volumes of the chlorine atoms in¬ 
crease as they accumulate in molecules of the above type . 

As an alternative to the above, we may assume that two 
chlorines possess volumes of Cl = 21*5 and two of volumes 
Cl = 23 o. The above assumption is, however, the simplest. 

Bromine Br. 

The free value according to Thorpe is— 

2[Br] = 2 x 2674. 

In the monobromides we find— 

Substance. V . 2 *V a (R). A. 

CH 8 Br 557 260 297 + 2*6 

This positive value represents the excess above that which 
may be considered normal. 

TABLE XXXVII. 


Substance. 

Vm. 

R. 

Br. 

C 8 H 7 Br . . 

9 T 3 

70*0 

27*3 

C 4 H 9 Br . 

118*6 

92*3 

26*3 

C 8 H ai Br . 

141*2 

114*1 

27*1 


The average volume of bromine is about 
[Br] = 27*0, 


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8o 


LIQUID CHEMICAL COMPOUNDS, 


The Poly bromides. 
TABLE XXXVIII. 


Substances. 

V m . 

Br. 

R-Br . 


26*9 (average) 

CH 2 Br a . 

77*6 

27*7 

CHBr 3 . 

103*5 

28*3 

CBr 4 

(Not studied) 

(probably larger) 

Mean value . 

. 27*6 


The observation that the substitution of a negative atom for 
a positive one involves an increase in the atomic volume, is 
repeated in the polybromides, provided these halogen atoms are 
attached to the same carbon atom. 

The values for bromine which have been shown, increase pro¬ 
gressively as the number of such atoms united to a single carbon 
atom increases. The volume of bromine may, as already indi¬ 
cated, tend to a higher value, viz. 28 o or even 28*5. 

The following compounds are noteworthy :— 

CBrClg 108*4 CC1 8 8o*8 Br 27*5 

POBrClj 107*38 POClg 101*37 - 22*0 = 79*37 Br 28*0 


Cl 

Br 

1 


Cl—C—Cl 

1 

H—C—Br 

1 


Cl 

1 

Br 


[Cl] = 22*2 

[Br] = 28*3 


Cl—Hg—Cl 
[Cl] = 22*1 

Cl 

Br—Hg—Br 
[Br] - 28*5 

Br 

[Hg] = 18-9 

1 

ci—Si—Cl 

1 

| 

Br—Si—Br 

1 


Cl 

[Cl] = 22*2 

Br 

[Br] = 28*0 

[Si] = 34-0 


These numbers show that in an ordinary chloride or bromide, 
the value for chlorine is 22 T, and that for bromine 28*0. 

One remarkable exception is found, viz. P Br 3 . 


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ORGANIC COMPOUNDS CONTAINING THE HALOGENS. 81 


Br 


Br—P 


> 


P 27‘0 
3Br 84*0 

2nV a liro 
Vm 108*3 


Br 


A = - 27 


The volume of bromine is seen to be smaller than in most of 
the other bromine compounds, in which it is 28*0. 

If we suppose that 

[Br] = [P] = 27*0, then 
2«V« = [P] + 3[Br] = 27*0 x 4 = 108*0 

The similarity between the combined volumes of phosphorus 
and bromine is probably accidental. The important point to 
notice is that the three bromine atoms assume similar volumes to 
the value in R - Br, which has been shown to be 26*9. This 
involves a failure of the usual law of increase with the accumula¬ 
tion of halogen atoms about a single carbon atom for some reason 
or other. 


Iodine I. 

The free volume is according to Billet— 
2[I] = 2 x 33*5. 

Methyl iodide. 

CH 3 I V w = 63*9 
CH S 26*0 
I 37*o 

2«V a 63*0 
Vm 63*9 


A = + 0*9 


This result is in accord with those previously obtained for 
the other series, and is due to the presence of the methyl group 
as shown in the following table:— 


TABLE XXXIX. 


Substance. 

Vm. 

2 *V a . 

A. 

CH 8 - H . 

38*5 

29*6 

+ 8*9 

CH 8 -C 1 . 

507 

47*6 

3 ’ 1 

CH 8 - Br . 

557 

53 *° 

27 

ch 8 -i 

63-9 

63*0 

0-9 


6 


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82 


LIQUID CHEMICAL COMPOUNDS, 


These plus differences are found to diminish with the apparent 
size of the atoms, etc. They also diminish with the number of 
CH 2 groups, and thus they nearly disappear at about the third 
member of each series. 

The monoiodides are:— 


TABLE XL. 


Compound. 

V*,. 

Volume of 
the Hydrocarbon 
Radicle. 

I. 

V/W. 

CjHjI . . . 

85*8 

48*0 

37-8 

3730 

CjHjI . . . 

106*8 

70*0 

3 6*8 

3-683 

C.HjI. . . 

128*2 

92*0 

36*2 

3«3 

C 6 H u I . . 

151*4 

114*1 

37*3 

3693 

c«h 6 i . . . 

130*5 

92*8 

377 



Mean value [I] . 

37 *o 



The average value of iodine is— 

[I] = io[H] - 37*0, 

which is a relation enabling us to find the variation in the atomic 
volumes throughout the series. 

TABLE XLI.— Values of V/W in the Alkyl Iodide Series. 


Substance. 

w. 

Vm. 

V/W. 

CH,I . . 

17 

64*1 

3770 

CjH s I . . 

23 

85*8 

3730 

c,h 7 i . . 

29 

106*8 

3-683 

c 4 h,i . . 

35 

128*2 

3-663 

C,H U I . . 

4 i 

151*4 

3’693 


Several higher compounds have been studied by Dobriner, 
but the curve is not very regular. 

In this series, we note similar characteristics to those for the 
paraffins. 


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ORGANIC COMPOUNDS CONTAINING THE HALOGENS . 83 


(a) A gradually diminishing series of values to— 

(b) a minimum at the fourth or fifth member; 

(c) an increasing series of values after this minimum. 

A similar result is shown in Table XL, col. 4, so that the 
nature of the curve indicated by the values of V/W is the true 
one. 

In dealing with the halogens, we may include an inorganic 
series examined by Prideaux. 


HgCl a 63-3 
Hg 189 

cl* 44*4 

2*V a =63*3 


HgBr* 75*1 

Hg 18*9 
Br a 56*0 

2*V a =74*9 


Hgl a 928 

Hg 18*9 
I 74*0 

5«Va = 92*9 


The values of Cl, Br, and I are— 

[Cl] = 22*2 [Br] = 28*0 [I] = 37 # o. 

in an inorganic series. 

These are similar to those already shown for organic com¬ 
pounds. 

The average volumes of the halogen atoms are thus— 

V« [F] = 87 At. wt. 19*0 

[Cl] = 22-o „ 35*5 

[Br] = 28*0 „ 8o*o 

[I] = 37*0 „ 127*0 


In this family the atomic volumes increase with the atomic 
weights, but not proportionally. 


Constitutive Effects among the Halogen Compounds. 

The Combined Influence of a Halogen Atom and Iso 

Group. 

The effect of the branching of the hydrocarbon chain when 
halogen atoms are present, has now to be studied. 

Among the hydrocarbons (paraffins), a branching of the chain 
is, so far as we can see, uniformly accompanied by a contraction. 
If, however, one of the hydrogen atoms be substituted by a 
halogen atom, a different result ensues. The following table 
shows this. 

6 * 


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8 4 


LIQUID CHEMICAL COMPOUNDS, 
TABLE XLII. 


Chlorides, 

Vm, 

A. 

Vm. 

Iso, etc. Compounds. 

CH S . CH a . CH a . Cl . 

CH S . CH a . CH 2 . CH a . Cl 

CH S . CH 2 . CH 2 . CH a . CH 2 C 1 . 

917 

1127 

135*3 

+ 2*6 
+ i*8 

-0*5 

94*3 

114*5 

134*8 

(CH 8 ) 2 CHC 1 . 

(CH 8 ) 2 . CH . CH 2 C 1 . 
(CH s ) 2 .CH.CH 2 .CH 2 .C 1 . 

Bromides, 

CHj . CH 2 . CH a . Br . 

CH S . CH 2 . CH a . CH 2 . Br 

CHj . CH 2 . CH 2 . CH a . CH 2 Br 

97*3 

118*6 

141*2 

+ 2*2 
+ 1*0 
-0*4 

99*5 

ng*6 

138*8 

(CH 8 ) 2 . CHBr. 

(CH 8 ) 2 . CH . CH a Br. 

(CH 8 ) 2 . CH . CK a . CH a . Br. 

Iodides, 

CH S . CH a . CH 2 . I . 

CH 8 . CH a . CH 2 . CH a . I . 

CH S . CH 2 . CH 2 . CH* . CH 2 I . 

107*1 

128*2 

151*4 

+ i *5 
+ 0*2 
- 0*3 

108 *6 
128*4 
151*1 

(CH 8 ) 2 CHI. 

(CHI, CH . CH a . I. 

(CH s ) a . CH . CH 2 . CH a . I. 


We see that in the case of the propyl and butyl halogen 
compounds, the iso or branched chain derivatives are larger than 
those with straight chains. Exceptions to this are found among 
the amyl compounds, which show contractions approximately 
equal to that for the iso-group. 

The positive differences thus seem to be connected with an 
approach of the halogen atoms to the iso-group. 


Amyl chloride (iso) 


Butyl chloride (iso) 


Propyl chloride (iso) 


CH, 


CH—CH,—CH,—Cl 

Ah, 

or CH,—CH—CH,—CH,—Cl 


i 


H, 


CH,—CH—CH,—Cl 

Ah, 

CH, . CH . Cl 


Ah, 


A - 0*5 


A + I‘8 


A + 2-6 


The inference is, that the approximation of a halogen atom 
to a methyl group causes an expansion which diminishes as the 
two groups become separated, until, when sufficiently removed, 
the contraction for the iso group alone remains. 

We have thus to admit the possibility of the interaction of groups 
not directly connected by valency linkings . 

Whatever be the exact cause of the expansions, it would seem 


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ORGANIC COMPOUNDS CONTAINING THE HALOGENS. 85 


that they take effect on the halogen atoms, that is, their volumes 
increase by the values J. Thus in the compounds 
CH 8 - CHX - CH 3 , [Cl] - 21-5 + 2-6 = 24-1, [Br] = 27-0 + 2*2 = 29*2, [I] = 38*5 
This fact is proved by an examination of the compounds 
of formula 

CH 3 - CXj - CH 8 (CH a ) x d 16 = ri<>58, C = 0*50 

from ch 8 .ci.chh 

Vm 114*8 
2CH 8 52*0 
C 14*8 


66*8 
Vm 114*8 

2[C1] = 48*0 

[Cl] = 24*0 

(CH 8 ) 2 CBr 2 , do 1*8149, b.p. 114*0, C = 0*463 
from CH 3 . CH 2 Br. CH 2 Br 

V w 126*4 
Vm 126*4 

(CH 8 ) 2 C 66*8 

2[Br] = 59*6 

[Br] = 29*8 

These facts are of the greatest importance. They show that 
an atom may have more than one value according to its position, 
in a hydrocarbon chain. 

Calculation shows that the above expansions are much aug¬ 
mented in compounds containing the tertiary group— 


ch 3 —ch 9 — 
<!:h. 


a, /?, and y Halogen Compounds—Partial Rings. 

The di- and tri-substituted paraffins in which the halogen 
atoms are attached to a single carbon atom 

e.g. CH 3 X, CH 2 X 9 , CHX 3 , CX 4 
CH s . CH a X, CH 3 . CHX,, CH 8 . CXg 

have been studied. 

In all of these a compounds the additive rule is approxi¬ 
mately realized. Other compounds, however, occur, in which 
the halogen atoms are attached to different carbon atoms, e.g. 
X - (CH 2 ) w - Y. 

This mode of distribution is found to be accompanied by 
very considerable modifications in volume. 


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86 


LIQUID CHEMICAL COMPOUNDS. 


TABLE XLIII.— Polyhalogen Compounds. 
a, j 3 , and y derivatives. 


a Compounds. 

V m or 2 n V a . 

A. 

Vm. 

a, £, etc., Compounds. 

CH, . CHCl, 

CH, . CH, . CHCl, . 
CH, . CHBr, . 

CH,. CHC1I . 

88*96 

2»V a iii’o 

-3*6 
- 3* 1 

85-3 

107-9 

CH,C1. CH,C1. 

CH, . CHC1. CH,C1. 


100*2 

-3*i 

97*06 

CH,Br . CH,Br. 


103*6 

-2*6 

101*0 

CH,C1 . CH,I. 

CH, . CH, . CHBr, . 

»» 

122*4 

-3*2 

119*2 

CH, . CHBr . CH,Br. 

CH,. CC1, . . 

»» 

107*0 

-3*3 

103*7 

CH,C1. CHCl,. 

C,H,C1 4 . 


125*4 

-60 

119*4 

CHC1, . CHCl,. 

C,HC1, . . . 


1438 

-5*6 

138*2 

CHCl, . CCl,. 

C,C1 4 .... 


118*0 

-3*2 

114*8 

CC1, : CCl,. 

CHBr : CHBr. 

C,H,Br, . . 


93*<> 

-1*6 

9i*4 

CH, . CH, . CHCl, . 
CH, . CH, . CHBr, . 


111*0 

122*4 

-5*0 

-4*3 

H H 

s»& 

H 6 

CH,C1 .°CH,. CH,C1. 
CHjBr . CH, . CH,Br. 


It is evident from the above that 

(a) A halogen atom in the (/*) position, counting from the 
end of the carbon chain, occasions a contraction of 3 units, but 
only if one or two halogen atoms are found in the (a) position. 
Halogen atoms in the (a) position alone or in the Q8) position 
alone do not cause contractions (vide ante). 

( b ) Given the requisite number in the (a) position, the con¬ 
traction depends upon the number in the (£) position. This is 
seen from the fact that in tetrachlor and pentachlor ethane, the 
contractions are double, or amount to 6 0 units. 

Conclusion : The only explanation which we can give to the 
above facts is, that there is some sort of interaction between the 
two chlorine atoms, which is due to their being contiguous. 
This necessitates such an arrangement of the atoms as to allow 
of this, and the contraction depends upon the number of groups 
in the partial ring. 

This is shown by means of the plane formulae as follows:— 


Ethidene chloride. 
Cl 


CH 


4 , 


H 


Ethylene chloride. 
CH 2 -Cl x. 


CbU 


-Cl 

A = - 3 * 6 . 


\ 

1 

1 

/ 


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ORGANIC COMPOUNDS CONTAINING THE HALOGENS . 87 


Propidene chloride. 
Cl 

Cl 


Propidene chloride. 

ch 2 - a \ 

I ) 

CH -Cl' 7 

I 

CH3 

A = - 3 * 1 * 


Trichlor ethane. 

Cl-CH-CK 


iH., 


-Cl*' 


Trichlor propane (chlorhydrin). 

CII 2 - 01 \ 


CH - 

cl 2 - 


-Cl 


*ci' 


A = - 3*1. 


A = - 6*0 probably. 


See Chapter II, p. 52. 

Tetrachlor ethane. Pentachlor ethane. 

/C\ -CH- CB n ,,C1-CH- C\\ 


\ 


a 


CH- 


gi 


'Cl- 


cr 


A = — 6*0. 


Cl 

A = - 5 * 6 


(^r) If we study the trimethylene derivatives, we find that 
the contractions are largely increased. Since the removal of a 
halogen atom to the 7 position would separate it from the one 
in the a position, and the large contractions indicate a correspond¬ 
ing interaction, we must suppose that the configuration of the 
hydrocarbon chain is modified in accordance with these results. 

This involves an arrangement of the carbon atoms on a curve, 
or the formation of a partial ring. 



A =-5.0 ^ = -4.3 

Although the result is doubtless due to an approximation of 
the halogen atoms, it seems clear that all the atoms share in the 
above modification. Probably 8 and e compounds would show 
still larger contractions, 


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88 


LIQUID CHEMICAL COMPOUNDS, 


(d) The presence of an ethenoid linkage influences the amount 
of the contraction. 

It has been shown that in compounds CH 3 . CHX . CH 3 and 
CH S . CX 2 . CH 3 , as compared with CH 3 . CH 2 . CH 2 X and 
CH 3 . CH 2 . CHX 2 , X being halogen atoms, etc., the volumes of 
these atoms are larger in the /8 position than in the a . It follows 
that if there is a contraction when one appears in the a and also 
one in the /8 or 7 positions, it must be due to some relation 
between these contiguous atoms. 

Since in the ay compounds, the contractions are greater than 
in the that is, when they are farther removed, the large con¬ 
tractions can only be attributed to a change in the configuration 
of the hydrocarbon chain brought about by the interaction of the 
terminal atoms. 


The Volumes of the Unsaturated Polyhalogen Compounds. 

There are evidences that on passing from the saturated to 
the unsaturated polymethylenes, a constitutive change takes 
place, which is connected with the combined influence of the 
olefin link and the halogen atoms. Only one or two data, how¬ 
ever, exist, so that it is scarcely possible to obtain that extent of 
view which leads us to certain conclusions. It will be thus 
necessary to resort to calculation to supply the deficiency to 
some extent. 


Chlorides. 


Ethyl chloride Vm. 
CH 8 — CHjCI 717 


Vinyl chloride Vm. 
CH a = CHC 1 — 


Ethylidene chloride. 

CH S —CHCl a 88*9 (obs.) 

C = 0*46 89*0 (by form.) 


A = 8*9 for H a 


Unsymm. dichlorethylene. 
CH a = CClj, 79*9 (obs.) 

8o*i (by form.) 


Ethylene chloride. Symm. dichlorethylene. 

CH a Cl—CHC 1 85-3 (obs.) CHC 1 = CHC 1 — 

C = 0*46 85’6 (by form.) 


Acetylene tetrachloride. 

CHClj—CHC 1 2 — 

120*6 (by form.) 

A = 5*6 for Hj, 


Tetrachlorethylene. 

CC 1 2 = CC 1 2 114*8 (obs.) 

115*0 (by form.) 


Propylene chloride. 
CH 3 —CH 2 —CH^Cl 91*7 


Allyl chloride. 
CH 2 =CH—CH 2 C 1 85*0 

A = 6*7 for H 2 


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ORGANIC COMPOUNDS CONTAINING THE HALOGENS . 89 


Ethyl bromide V«. 

CH,—CH a Br 77 # i (by obs.) 


nsymm. dibromethylene. 
CBr, — 


Bromides . 

Vinyl bromide V m . 

CH a = CHBr 71-3 

: 5*8 for H a 

Ethyledene bromide. Uns 

CH,—CHBr, — CH, = CBr, 

98*8 (by form.) 93*0 (by form.) 

A = 5*8 for H a 

Ethylene bromide. Symm. dibromethylene. 

CH a Br—CH,Br 97-1 (obs.) CHBr = CHBr 91*4 (obs.) 

97*1 (by form.) 91*3 (by form.) 

A = 5*8 for H a 

Tribromethane. Tribromethylene. 

— CHBr = CBr a — 

119*3 (by form.) 113*6 (by form.) 

A = 5*7 for H a 

Propylene bromide. Allylene bromide. 

CH a —CH a —CH a Br 97*3 (obs.) CH, =» CH—CH a Br 90*8 (obs.) 

A = 6*5 

In the above table, we have a summary of the results for the 
unsaturated polyhalides. We find in the derivatives of ethane a 
difference of 5 7 for H 2 . 

normal A for H a 7*4 
actual A for H a 5*8 

change in value 1*6 

From this we conclude that there is an increase of v 6 in the 
volume of the unsaturated compound, presumably owing to the 
close association of the halogen atom or atoms with the olefin 
links |= | 

Acetylene tetrachloride. 

CCl a - CCl a 


Cl—C—Cl 
II 

Cl-C—Cl 


2 [C] = 29*6 
4 [Cl] = 88*8 

118*4 

for part, ring 5*2 
113*2 

for unsat. +1*6 


2»Va 114*8 
Vm 114*8 


Vinyl bromide. Unsymm. dibromethylene. 

CH, = CHBr CH a = CBr, 


CH,—CH a Br 

77*1 

Br CH,—CH a Br 

98*8 

less 2H 

7*4 

CH, = C less H, 

7*4 

for unsat. 

69*7 

for unsat. 

91*4 

+1*6 

+ i*6 

2 nV a 

7 i '3 


93*0 

Vm 

7 i # 3 

v w 

93-0 


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9 ° 


LIQUID CHEMICAL COMPOUNDS, 


Symm. dibromethylene. Tribromethylene. 


CHBr = CHBr 

CH—Br 

II 2CH 37-0 

CH—Br 2Br 56*0 

CHBr=CBr a 
Br—C—Br 2C 

II H 

CH—Br 3Br 

VO t>* 

for part, ring 

93 *o 
- 3-2 

for part, ring 

117-3 
- 3‘2 

for unsat. 

89-8 
+ 1*6 

for unsat. 

114*1 
+ r6 

2 »Va 

Vtn 

91*4 

9**4 

2»Va 

Vm 

115*6 

113*6 



or better 
Tribromethane 
CH a Br—CHBr a 
less 2H 

119*3 

- 7*4 



for unsat. 

1 ii*9 

+ i*6 



2»Va = 

V = 

H 3*5 

113*6 


The following show scarcely any effect for unsaturation :— 


Ally! chloride. 
CH a = CH—CH 2 C 1 
C,H b 62-9 
Cl 22*1 

2rtV a = 85*0 
Vm = 85*0 


Allyl bromide. 

CH 2 = CH—CH s Br 
C3H5 62*9 
Br 28*0 

2«Va = 90*9 
Vw = 90*8 


From the above, we conclude, that, in the unsaturated group 
—CH=CX— 

where X is a negative atom like Cl, Br, etc., there is an ex¬ 
pansion of + 1 *6. Since this expansion remains the same what¬ 
ever be the number of halogen atoms present, we are probably 
right in connecting it with the presence of the olefin linkage | = |. 

In allyl chloride, for example, such a feature is not noticed. 
This shows that if the halogen atom be sufficiently separated 
from the olefin link no expansion occurs. 

In considering this explanation, we are led to find in it a 
reason for a somewhat similar phenomenon connected with the 
—C = O group. 

In the aldehydes, 

H 

/ 

R—C 

% 

O 


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ORGANIC COMPOUNDS CONTAINING THE HALOGENS . 91 


we shall find that the volume of O" is 7*4 (Chap. IV.), but in 
certain other compounds, which involve the substitution of 
hydrogen by chlorine, hydroxyl, and other negative groups, we 


find a considerable 
Thus in— 

expansion. 


Cl 

OH 

OR' 

/ 

/ 

/ 

R—C 

R—C 

R—C 


\ 

\ 

O 

O 

O 

Acid chloride. 

Acid. 

Ethereal salt. 


the volume of O" is 11 1, so that there is an expansion of + 37 
as compared with O" in the aldehydes. Again we notice that 
similarly there is unsaturation in the C = O group, as in the 
—C = C— group. 

We may thus suppose that these expansions are due to a 
similar cause in the two cases. It is, moreover, not improbable 
that certain well marked variations in the atomic volumes of 
certain elements, which like oxygen show two or more values, 
may also be due to the co-existence of unsaturation and negative 
groups. 

It must be observed that unsymmetrical dichlorethylene 

CH a - CCla 

is exceptional, in that there is a contraction instead of an 
expansion* We do not propose at present to do more than 
record the fact, as it is evident that we need much more 
varied and numerous data before we can deal adequately 
with the subject or come to certain conclusions. It is pos¬ 
sible that a repetition of the determination of the volume of 
unsymmetrical dichlor ethylene and the determination of the 
volume of symmetrical dichlor ethylene might show different 
results. 

General Remarks on Saturated and Unsaturated Poly halogen 

Compounds . 

The following represents a comparison of the contractions 
in saturated and unsaturated derivatives. 

* This seems to be due to the fact that the CH S group in CH S . CHC1 2 is 
unusually large. 


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92 


LIQUID CHEMICAL COMPOUNDS. 


CH 2 -CK 

I 


c 

-CH- 

1 

-Cl 

• / 
ch 2 Cl' 


\ 

\ 

\pi_ 

1 

_ _ r* 11 

1 



vl — 


- 

A = - 3-6 



A = — 6.0 


A = - 3*6. 


A = 

- 6’o. 


CH—Cl 

Cl—c—Cl 


Cl—c—Cl 


II 

II 


II 


CH—Cl 

CH a 


0 

1 

0 


> 

II 

l 

ui 

A = - 1*3. 


A = - 2*6. 



In regard to (2), we must also note the possible existence of 
geometrical isomers, so that we might have 


CH—Cl 

II and 

Cl—CH 

Fumaroid form. 


CH—Cl 

II 

CH—Cl 
Malenoid form. 


Precisely how these differ as regards volume is not quite 
certain at present, but there is evidently here a rich field for 
future research. 

Applications of the above principles to a study of more com¬ 
plex compounds are indicated by the following. 

We have noticed the following effects. 


CH 8 

£h—1 

1 

ch 8 



C,H 7 

70*0 

ch 8 
| 8 

c 3 h 7 

70*0 

Cl 

Cl 

22*1 

CH-Br 

1 

Br 

28*0 


Wm 

92 # I 

94*6 

ch 8 

2 nV a 

v,» 

98- 0 

99 - 5 


A 

+ 25 


A = 

+ i *5 


Thorpe 82 has given a volume of V w = 142*6 to the following 
compound. 


Isobutylene bromide. 



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ORGANIC COMPOUNDS CONTAINING THE HALOGENS. 93 


C 4 H 8 4 X 22*1 

88*4 

or 



2Br 

56*0 


2CH3 

52*0 


. .- 


C 

14*8 


144*4 


CH 2 

22*1 

less iso group 

-0*5 


Br' 

28*Of 




Br" 

29*2f 


143 *9 



.. ■ 

Br atom and iso group 

+ 2*0* 



146*1 





- 3 *i 


145*9 



■ ■■■ 

For partial ring 

- 3 *i 



143*0 


■ ' ■ 


iso struct. 

-o *5 

SnVa 

142*8 




V m 

142*6 



142*5 


TABLE XLIV.— Aromatic Haloqrn Compounds. 


Substance. 

Vm. 

2»Va. 

A. 

C.H.F . 

101*6 

n6*o 

— * 4*4 

C.HjCl . 

114*6 

129*1 

“ 14*5 

C.H.Br . 

120*0 

135*3 

- 15*3 

C.H.I . 

1307 

144*3 

-13*6 

Mean value . 

• 

- 14*5 


There is associated with these compounds the normal con¬ 
traction of - 14*5 f° r the ring, from which it follows that the 
volumes of chlorine, bromine, and iodine are not very different 
from their volumes in paraffin derivatives. 

The volume of— 

C 6 H 6 - is 96-0 - 3*2 = 92*8 
and of C 6 H 4 = is 96*0 - 2 x 3*2 = 89*6. 

The halogens in these aromatic compounds can be shown to 
have nearly the same volumes as in the aliphatic compounds R - X 

Cl sb 114*6 - 92*8 = 21*8 
Br = 120*0 - 92*8 = 27*2 
I = 1307 - 92*8 » 37*9 

In open-chain compounds 

Cl = 21-5 
Br = 27*0 
I = 37*o 

* The value of A found was 1*5 for association of Br and iso group. The value 
of - o*5 for the iso group should be added, so that the full value for the former con¬ 
stitutive influence is + 2*0. 

+ See Table XLII. The volumes of the bromine atoms ate taken as 
[Br] = 270+ A. 


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94 


LIQUID CHEMICAL COMPOUNDS. 


There is, however, indication of a slight increase from Cl to I, 
possibly due to the unsaturation of benzene. 


TABLE XLV.— Other Aromatic Halogen Compounds. 


Substance. 


2»V a - R. 

A. 

1.: 4 C 6 H 4 (CH,)C1 . 

I 35’3 

137*3 

-2*0 

C fl H 5 . CH a Cl . 

I33’8 

136-5 

-27 

C fl H 5 . CHC1 2 . 

1547 

154-6 

— 

1: 2 C a H 4 (.CH 8 )Br . 

I42-I 

142-7 

— 


Some of these results are unusual, since o compounds usually 
possess contractions and p compounds do not, but the data are not 
sufficient to enable us to account for them. Compounds of the 
type of o y nty and p dihalogen benzene derivatives have not yet 
received attention. 


The Gradual Chlorination of the Benzene Molecule. 

This very interesting question can be studied owing to the 
work of Jungfleisch. 88 

The volume of C^H^ is 96*0, and every atom of hydrogen 
subtracted involves a loss in volume of 3*2. 


Cl 

\/ 

ci 

D 

Cl 

Cl 

/\ 

\/ 

Cl 


vCl 


Monochlorbenzene , C 6 H 5 C1. Vm 114*6 b.p. 132 
(Unsymmetrical or odd) 

Cl «. C 6 H b C 1 - C 6 H 6 = 114-6 - 92-8 = 21-8. 

1: 4 Dichlorbenzene , C 6 H 4 Cl a . Vm 130*9 b.p. 172 
(Symmetrical or even) 

Cl 2 = 130*9 - 89 6 = 41*3. 

1:2:4 Trichlorbenzene , C 6 H 3 C1 8 . Vm 149*1 b.p. 213 
(Unsymmetrical or odd) 

Cl s = 149*1 - 86*4 =» 627. 


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ORGANIC COMPOUNDS CONTAINING THE HALOGENS . 95 


1:214:5 Tetrachlorbenzene , C 6 H 2 C 1 4 . Vm 164*8 b.p. 244 

(Symmetrical or even) 

Cl 4 = 164*8 - 83*2 = 8i*6. 

1:2:3:415 Pentachlorbenzene , C 6 HC 1 5 . Vm 183*9 b.p. 276 
(Unsymmetrical or odd) 

Cl 6 = 183*9 - 80 0 = 103*9. 

Hexachlorbenzeru , C 6 C1 6 . Vm 200*0 b.p. 326 

(Symmetrical or even) 

Cl 6 = 200*0 76*8 a 123*2. 

The average volume of chlorine is 20*0 in all the compounds. 
A close study of the results, however, shows that the chlorine 
atoms are not equal in volume, but that each pair involves a loss 
of about 2*3 or 2*5. 34 

TABLE XLVI. 


Substance. 

Monochlorbenzene 

c,h 5 ci 

V*ci. 

21*8 

A. 

(Unsymm. or odd). 

/-Dichlorbenzene 

C.H.CIj 

4 i *3 

I 9‘5 

(Symm. or even). 

Trichlorbenzene 

C.H.Cl, 

62*7 

21*4 

(Unsymm. or odd). 

Tetrachlorbenzene 

C.HjCl. 

8i*6 

18*9 

(Symm. or even). 

Pentachlorbenzene 

C e HCl„ 

103*9 

22*3 

(Unsymm. or odd). 

Hexachlorbenzene 

C.C 1 , 

123*2 

19*3 

(Symm. or even). 


There is thus a distinction between the Cl atom on one side 
of the molecule, and the Cl atom in the para position with 
reference to it, or the two atoms on opposite sides of the ring 
involve a contraction of 2*6 on the average. 

Thus we have 


1st Chlorine Cl* 
2nd Chlorine Cl 11 
3rd Chlorine Cl* 1 * 
4th Chlorine Cl iv 
5th Chlorine Cl v . 
6th Chlorine Cl vi 

Mean values 


rABLE XLVII. 


Normal. 

Abnormal. 

21*8 

— 

— 

19*5 

21*4 

— 

— 

18*9 

22*3 

— 

— 

x 9*3 

21*8 

19*2 


A = 2*6 



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96 


LIQUID CHEMICAL COMPOUNDS ,. 


The smaller values apply to the chlorine atoms marked 
in the following diagram. 


\ 

\ 




and the apparent result is that one-half of the chlorine atoms 
differ from the other half. 


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CHAPTER IV. 


THE MOLECULAR VOLUMES OF ORGANIC COMPOUNDS 
CONTAINING OXYGEN. 


The Volumes of Oxygen. 


KOPP (loc. cit.) recognized the existence of two different values 
for oxygen— 

Hydroxyl O' 7*8 
Carboxyl O" 12*2. 

The numbers are not very different from those now advocated, 
but it is necessaiy frequently to suppose that the volume of 
oxygen is not always one of those just indicated. Owing per¬ 
haps to constitutive influences several other values are also found 
necessary. 

The volume of free oxygen at the boiling-point is, according to 
Olszewski, Ber. 17 ref. 198, about 14*0 density (it 10 to IT 37). 

V (O: O) = 28-0. 

From the critical data, 


Tq = 155. Pc = 50 atmos. b.p. = 92, 


we find by D. Berthelot’s formula— 

v _ M iriTo* 

D “ P c (2Po - T) 


24*4 for O a . 


The atomic volume of free oxygen will be found to be 
greater than that of any of its combined values. 


Compounds of Oxygen. 

Among the simple compounds of oxygen is water H a O, 
which, contraiy to expectation, finds its place at the head of the 
symmetrical ether series. 

H-O-H CH3-O-CH3 

Vm(HjO) = 18 9 [O] = 18*9 - 2 x 37 = 11*5 

Hydrogen dioxide H - O = O - H Vm = 23*4 
2[0 iv ] = 23*4 - 7*4 = i6’o. 

Thus [O iv ] = 8-o t 

97 7 


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9 8 


LIQUID CHEMICAL COMPOUNDS. 


This compound seems to contain two hydroxyl groups—a 
fact which is deduced from the diminished volume of oxygen. 

A similar diminution is also seen in the alcohol series. 


TABLE XLVIII.— The Alcohols C»H a »-fiO'. See Le Bas, Ref. 85 


Compound. 

V m . 

A. 

V*. 

The paraffins. 

C 3 H 7 OH 

8i*4 

7*4 

74*0 

c,H 8 . 

c 4 h 9 oh 

102*1 

6*i 

96*0 

c 4 h 10 . 

c 6 h u oh . . 

1237 

5*9 

117*8 

C,H U . 

C 6 H 18 OH . . 

146*4 

6*5 

139*9 

c,h m . 

c 7 h 15 oh . . 

168*7 

6*1 

162*6 

c,h m . 

Mean . 

6*4 




The volumes of the simple compounds methyl and ethyl 
alcohols are somewhat different from the volumes they would 
possess, if they were strictly comparable with the succeeding 
members of the series. This feature seems to be common to all 
homologous series both in the case of molecular volumes and for 
numerous other physical properties also. 


Alcohol. 

v w . 

2«V*. 

A. 

CH S . OH 

42*8 

36*0 

+ 6*8 

C 2 H 8 . OH 

62*1 

58*2 

+ 3*9 

C 8 H 7 . OH 

81*4 

81*4 

— 


The effect of adding the group CH 2 a number of times, is 
similar to that observed when progressively large atoms like H, 
Cl, Br, and I are added to the radicle CH 8 , as already shown. 

This effect, in a wide sense, may be considered to be due to 
differences in complexity, or to increase in volume, and it prob¬ 
ably indicates the existence of differences between the internal 
forces of affinity in the different compounds. At any rate it 
shows that there are such differences in the distribution of force 
in the various compounds, that they are not strictly comparable 
at the boiling-point. These features repiesent slight differences 
in constitution existing. 

We have supposed that the relation 
[C] = 4 [H] 

holds in the paraffin series. 


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ORGANIC COMPOUNDS CONTAINING OXYGEN, 


So there is every reason to suppose that the relation 
[O'] = 2[H] 

is true in the alcohol series. The evidence is as follows :— 

Propyl alcohol C S H 7 0 H 81*46 = 11 x 7*405 
Allyl „ C 3 H 6 OH 74*08 = 10 x 7*408 

A for H a = 7*38 

If we consider 2[H] to represent a volume of 7*4, then 
hydroxyl oxygen also possesses this volume. 

Whether this is exactly so or not, the utilization of this 
relation enables us to find the variation in the atomic volumes in 
series of compounds like that of the alcohols. In calculations it 
is better to use the value [O'] = 6*4. 


The Branched Hydrocarbon Chain. 

TABLE XLIX. 


Normal Compounds. 

Vm. 

A. 

v,». 

Branched Chain 
Compounds. 





ch 3 


CH 3 . CH a . CH 2 . OH . 

81-46 (Sch.) 

-0*54 

80*92 (Sch.) 

ch 8 

-CH(OH). 



+ 0*49 

82-97 (Z) 



CH 3 . CH a . CH a . CH a . OH 

101*79 (Sch.) 


101*86 (Sch.) 

CH„ 



102*11 (Z) 



ch 3 

CH . CH a (OH). 





ch 3 i 




0 

p 

w 

+ 

102*8 (Th.) 

CH, 

C(OH). 





CH, 

CH 3 . CH a . CH a . CH a . OH 

123 6 (Z) 

-0*50 

123*1 (Sch.) 

ch 3 





123*6 (Th.) 

ch 3 

CH . (CH 2 ) 2 OH. 





ch 3 

! 



- 2*20 

121*4 (Th.) 

ch 3 

,C.(OH)CH 2 .CH 3 . 





ch 3 . 

• CH a ] 



- 1*60 

122*0 (Th.) 

ch 3 

VCH . CH a OH. 

CH 3 . (CH a ) 6 CH a (OH) . 

190-9 (Z) 

+ 0*6 

191*5 (Sch.) 

ch 3 

. CH(OH)C 8 H 13 . 


These results are most contradictory, a fact which is rendered 
more evident by the observation that the data due to different 
observers sometimes show positive, and sometimes negative 
differences. 

It follows, that no general rules can be drawn up which would 
indicate the connexion between these differences and the position 

7 * 


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IOO LIQUID CHEMICAL COMPOUNDS . 

of the OH group in the chain, or its position relative to the iso 
group. 

It is at present difficult to understand the reason for such 
differences. 

The butyl alcohols of Thorpe indicate a close relationship 
between the position of the (OH) group and that of the iso group. 

In these instances we are able to state that the minus differ¬ 
ence is greater the nearer the (OH) group is to the iso group. 

The following consideration emphasizes the difficulties at¬ 
tending a satisfactory explanation of the above results. This is, 
that there are possibly three overlapping constitutive effects 
which, moreover, may not be quite independent:— 

(a) The effect of the branched chain. 

( b ) The position and influence of the (OH) group. 

(c) The influence of the (OH) group on the iso group. 

A re-determination of all the values by one observer, and a 
more extended body of data would doubtless clear up these 
difficulties. 


Partial or Incomplete Rings . 86 
a/? and ay Compounds. 

TABLE L. 



Compound. 

Vm. 

2„V a . 

A. 

Ethylene 

Glycol CH a (OH) . CH a (OH) 

64-9* 

66*4 

-i *5 

Propylene 

„ CH 8 . CH(OH) . CH a (OH) 

85-4 

88*4 

-3*o 

Trimethylene „ CH,(OH). CH, . CH a (OH) 

8,f2 

ft 

“ 4*2 


These compounds are analogous to the a /3 and ay halogen 
compounds, and the values of A are :— 


CH3-CH 


CH 2 

/ 

ch 2 

\ 

ch 2 - 


CK 


ch 2 — 
A — — 3»i 


^ = —4.3 


CH 3 — CH 


— Cl" 

CH 2 — 

A = — 3.0 

Brx 

ch 2 — 

\ 

/ 

1 

1 

/ 

/ 

ch 2 

\ 

Br'' 

ch 2 - 


-OH n 


OH' 


-OH > 


•OH'' 


^ = -4.2 


* This value due to Ramsay is probably too large, thus making the value of A 
too small. 


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ORGANIC COMPOUNDS CONTAINING OXYGEN ioi 


The contractions are thus due to particular configurations of 
the molecules which have been already noticed. They have been 
named partial or incomplete rings. 

The following conclusions are drawn:— 

(a) The a/8 are smaller than the ad compounds by about 

3 units. 

( b ) The ay are still smaller than the ad compounds by about 

4 units. 

The following compounds show how the atom : O contrasts 


with the halogens, and with the (OH) group in respect of its 

effect in the direction indicated. 



(i) Acetyl chloride. 

(2) Triacetyl chloride. 

Cl Cl 

Cl 0 

Cl 

CH S — i or CH 3 — (! = O 

1 II 

ci—C—C or 

0 

11 

°\ 
— 0 

1 

0 

II 

O 


i, t, 

V» 74*0 (Thorpe). 87 

CH* 26*0 

C 14*8 

\m 125*5 (Thorpe). 

2C 

29*6 

4 C1 

88*4 

Cl 22*1 

: 0 n*o 

: O 

11*0 

— 

5nV a 

129*0 

2nVa 73*9 

Vm 

125-5 


A 

-3*5 

We see that the atom : O in 

opposition with 

a halogen atom 


does not produce the constitutive effect indicated, but that two 
halogens in opposition are capable of doing so. 

It is evident that in triacetyl chloride we have two adjacent 
chlorine atoms which produce the normal contraction. The 
association of the atom : O with Cl does not produce any very 
appreciable contraction, either owing to the small attraction 
between the two atoms, or because the double linking of the 
oxygen causes it to lack mobility. 

The formula for the compound in consequence might be— 


Oi 

I 


1 

pi _p 

_ P = A 

Vtl \J 

— u = u 

1 

il 

1 

Cl 


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102 LIQUID CHEMICAL COMPOUNDS. 

(3) Weger 88 has studied the volume of an a/8 compound of 
the same nature. 

afi dibrompropyl alcohol CH 2 Br . CHBr . CH 2 OH. 


b.p. 219 0 V m 124*3. 

Volume of CH 8 . CH 2 . CH 2 (OH) 

81-5 

less H 2 

- 7‘4 

plus 2 Br 

74*1 

56*6 

2 nV a 

130*7 

Vm 

124*3 

A 

-6-4 


The formulae which might conceivably apply are:— 


Br-CHo 

i 

(a) Br ^ 

i 

t 

ch 2 — o\i' J 


(b) 


ch 2 - 

- Br \ 

1 

) 

/ 

CH- 

-Br/ 


HO — CH. 2 


A = - 3-0 


— 3-0 


CH 2 

/ 

(c) Br-CH 

CHa 


A = - 4 • 5 



CH 2 - 0 H\ 

\ 

i 

/ 

CII-Br(^ 

\ 

\ 

I 

/ 

CH 2 -Br - / 

— 6.0 probably 


The first two, and possibly the third, are excluded by reason 
of the magnitude of the contraction. Compounds of the type 
expressed by the fourth formula have not been directly studied. 
These include the trichlor, brom hydrins. In order to ascertain 
the contractions to which these are subject, their volumes maybe 
calculated by the formula already given. 

Weger gives for a /3 dibrompropyl alcohol. CH 2 Br . CH 2 Bt . CH 2 OH. 
do 2*1682 b.p. 219 0 
dsi9 17535 

Thus C = 0*532. 

For trichlorhydrin, CH 2 C 1 . CHC 1 . CH 2 C 1 

we find d 16 1*3980 (Perkin) b.p. 156*0. 

: - Assuming the value C = 0*532, we find 


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ORGANIC COMPOUNDS CONTAINING OXYGEN. 103 


CH 2 

CH- 

1 

ch 2 


CK 


Cl 


Cl 


1 

/ 

N \ 

J 


Vm 124*2 

C 8 H 5 17 x 37*0 62*9 

3CI 66*3 

2nVa = 129*2 
Vm = 124*2 


A = -5*0 


For tribromhydrin, CH 8 Br - CHBr - CH 2 Br. 


CH 2 

CH- 

CH 2 


Br 


\ 


•Br 


/ 


•Br 


b.p. 220° 

Vm 


di 5 


sH 

3 Br 


ZnV a = 
Vg = 


A = 


2*4134 (Perkin) 
141*1 
62*9 
84*0 

146*9 

141*1 


- 5*8 


These trihydrins are evidently similarly constituted to the 
parent compound glycerol, and we are thus led to suppose that 
Weger’s compound possesses a similar constitution, by reason ot 
its contraction. 


CH 2 -OH>^ 

) 

I 

CH- 0 H(^ 

CH 2 -OH'' 

Glycerol. 

A few more of these compounds may now be studied, 

a dichlorhydrin CH 2 C 1 . CH(OH) . CH 2 C 1 


CjHjCl.O 

d„ 1-367 b.p. 174° C = 

0*535 


Vm =■ II2-7 


ch 2 - 

- CK 3CH ? 

66*6 


\ 2C1 

44*4 

1 

1 -O- 

/ 

7*4 

CH - 


ii8*4 

I 

\ By form. 

1127 

1 

ch 2 - 

-C\J A 

= -57 


The 0 dichlorhydrin CH 2 (OH) . CHC 1 . CH 2 C 1 has a slightly larger volume 
113*5, from which we obtain the difference A = - 5*1. 


CH 2 - 

-Br\ 

| 

\ 

1 


Br 7 



CH 2 - 

1 

1 

-OH^ 


Dibrompropyl alcohol. 


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104 


LIQUID CHEMICAL COMPOUNDS, 


i„> 

iff,! 


,OH 


Glycide - epihydrin alcohol C,H 6 O a . 

The value of C from epichlorohydrin is 0*46. 

do 1*165 b.p. 162 0 V m = 74*4 

3CHj 66*6 

14-8 (2 X 7-4) 


20 

5nVa 
fey form. 


81*4 

74*4 


A fofc ring = - 7*0 


A compound of this type has been directly investigated. 
Epichlorohydrin. 


CH,\ 

1 \n 

V m = 87*3 (Thorpe) 

CH / 

C 8 H 6 63*0 

Cl 22*2 

CHjCl 

O 7*4 

2 nVa = 92*6 
By Obs. = 87*3 



A for ring = -5*3 


These two compounds thus possess three-membered rings. 

It thus happens that the value of A for these ring compounds is 
similar to those which are constituted the same as glycerol. 
This is probably a coincidence only. It is, however, possible 
that part of this value may be due to the attachment of the 
group CH 2 C 1 to the ring, since a contraction occurs in the com¬ 
pound C c H 6 CH 2 C 1 for this reason. 

In conclusion we see from a study of their molecular volumes 
that the compounds have without doubt the formulae which have 
been given to them. 


Aromatic Compounds. 

TABLE LI.— The Phenols. 


Compounds. 

Vm. 

A. 

Vm. 

The Hydrocarbons. 

C 6 H 5 OH . . . 

101*9 

5*9 

96*0 

C 6 H 6 Benzene. 

*C,H<(CH,)(OH). . 

123*8 

5*6 

118*2 

C 6 H b (CH s ) Toluene. 

C.HjCHjOH . 

1237 

5*5 

»» 



Mean 

= 5*6 




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ORGANIC COMP 0 t/NDS CONTAINING OXYGEN 105 


The volume of - 0 - in the phenols is on the average 5*6, 
and thus is 6*4 - 5*6 = o*8 of a unit smaller than in ordinary 
alcohols. 

This difference indicates the existence of a special constitutive 
effect caused by the substitution of the aromatic nucleus for the 
alkyl group R, when the group (OH) is present. For C 10 H u O 
two values are given. 

(а) Ordinary thymol Vm 189*3 (Pinette). 

(б) Carvol (unspecified) 190*7 (Schiff). 

From the formula, which is that of thymol, 
we get the following calculated volume:— 

Cymene 184*6 

less H - 3*2 

181*4 

plus OH 9*3 (5*6 + 37) 

2«Va 190*7 

This is exactly the value given by Schiff It will be seen, 
however, that the (OH) group occupies the ortho position with 
reference to the isopropyl group, and this should occasion a con¬ 
traction of about 2 units. The normal volume thus is 1887 
approximately, which is similar to the volume given by 
Pinette. 

Moreover any other compound of formula C 10 H 14 O would 
still be subject to a similar contraction, for an OH group in the 
nucleus would necessarily occupy the ortho position with refer¬ 
ence to either the C 8 H 7 or the OH group. Thus the volume 
of any of these compounds would be in the neighbourhood of 
189*0. 

There is no reason to suppose that Schiffs value is due to 
experimental error, so that we are compelled to find some other 
reason for the larger volume. 

Remembering that the latter corresponds to a compound in 
which the paraffin and hydroxyl groups are independent, that is 
to 3»Va, only allowing for ring structure, we see that the ex¬ 
planation may lie in the fact that the groups are opposed. The 
structure of Pinette’s compound would be “ adjacent ”. 



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ORGANIC COMPOUNDS CONTAINING OXYGEN 107 


the value of Sn V a > and so results in one very nearly equal to 
that shown by V m . 

It is to be supposed that compounds like menthol C 10 H 20 O 

should agree with the characteristics of the class to which it belongs. 

Thujamenthol, 0*9015 b.p. 212 0*7389 C = 0*554 

V m = 211*1 (thymol) 

From thymol we find— 

Cymene H 14 184*5 

O' 5*6 

190*1 

less for ortho struct. - 2*0 

188*1 
6H 23*8 

2nV a = 211*9 
Vm = 211*1 by form. 


There is thus agreement with the formula— 


CH 2 —CH-OH 

/ \ / CH 

CH,—CH CH—CH< 

\ / XCH 

CH,—CH, 


3 

3 


This compound possesses a contraction of - 15*0 for ring 
structure, and a contraction of - 2*o for ortho structure, as for 
thymol. 


CH 


CH 


Dihydrocarveol c,.h 18 o 
djQ 0*927 b.p. 225 0 

2 CH 2 —CH—OH 

\ / \ 

C—CH CH—CH. 

/ \ / 

3 ch 2 —ch 2 


C = 0*550 

^386 °*74 I 

Vm 207*8 

JSnVa 222*0 

A - 14*2 for ring. 


This at once enables us to place dihydrocarveol and similar 
compounds in their particular class—the menthan terpene alcohols. 
A very interesting compound is— 


Cineol C 10 H 18 O. 


CH a 


CH 2 


CH. 


\ 


CH 

\ 


CH, 


1 


CH* 


CH* 


/ 

H 


This substance has the following formula 
ascribed to it:— 

C = 0*46 as is usual for ring compounds, 
b.p. 176 d 16 0*923 d 176 0*792 

Vm 194* 0 
2»V a 222*0 

A = - 28*0 (for ring). 


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io8 


LIQUID CHEMICAL COMPOUNDS . 


Cineol thus belongs to the bridged ring class. 

A compound of a similar character which has been specially 
studied is 


Borneol C 10 H 18 O. 


CH a -CH- 

CH,—C—CH a 

CH,- c!- 

<^H, 


■CH, 

-CH(OH) 


V w 190-5 

%Na 222-0 


A = - 31*5 for ring. 


The value of A for these compounds is about twice that for a 
single six-membered ring. 

It seems probable that minor overlapping effects may disturb 
the result somewhat. 


Thus 2 x - 15-0 *= - 30*0 for ring structure, 

and - x«5 for ortho position of CH 8 and OH. 

In accord with this, we find that camphor, a-CO compound, 
possesses a contraction of - 30 0 only. 


The Ethers. 

R—O—R'. 

Corresponding to the alkyl halogen compounds (halogen 
monovalent) 

R—Cl, R—Br, R—I 

we find the ethers ( divalent) 

R—O—R and R—O—R^ 
which involve the combination 

C—o—C. 

These give results which are different to those characteristic 
of the combination which has just been studied, viz.:— 

C_o—H. 

The following isomers of empirical formula C 6 H 14 0 exist— 

c 3 h 7 —o—c 8 h 7 C 4 H 9 —O—C 9 H 6 C 6 H u —O—CH 8 

¥ V 

Symmetrical. Unsymmetrical. 

Vm 151*3 I 50*3 149*5 

C 6 H l8 —O—H 
V m 1462. 

In the above compounds, there is a progressive change in 
volume from the symmetrical to the unsymmetrical types, and it 


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ORGANIC COMPOUNDS CONTAINING OXYGEN 109 

becomes smaller as the oxygen atom approaches the end of the 
chain. 

An analogous variation is found in the case of the boiling- 
points, but in the opposite direction. 

(1) (2) (3) ( 4 ) 

b.p. 907 91*4 — 157-0 

The last step of the change in boiling-point, that is, from the 
methyl ethers to the isomeric alcohols, is usually very great—about 
70° C. 

This corresponds to a volume change of 5 units. The follow¬ 
ing comparisons give the volumes of ethereal oxygen. The 
values of this atom are found by subtracting the volumes of the 
paraffins from those of the corresponding ethers. 


TABLE LII. 


The Methyl Ethers . 

The Symmetrical Ethers . 

The Paraffins . | 

Compound. 

v w . 

>0. 

Compound. 

v m . 

>0. 

C»Hjw + 2. 

v«. 




H— 0 —H 

18*9 

n *5 

cX 

[7*4] 




CH S —O—CH, 

627 

107 

[52-0] 

C a H 5 —0—CH 3 

84*2 

10*2 


C,H„ 

[74-0] 


CjH 6 —O—CjHj 

106*4 

10*4 

C,H l0 

96*0 

CjH 7 — 0—C H 8 

105*9 

9*9 




c 4 h 9 —0—ch 8 

C B H n —0—CH S 

127*5 

9*7 




C.H., 

117*8 

149*5 

9*6 

CjH,—O—C,Hj 

I 5 1 *3 

n*4 

c„h 14 

139*9 





c 7 h 16 

l62*6 




C*H,—O—C 4 H„ 

197-8 

n*5 

c 8 h i8 

l86 *2 


The mean value of ^>0 in the methyl ether series, is 9 9, 

and in the symmetrical series n*o. Also, there are similar 
variations in the two series, viz. first a decrease, and subsequently 
a gradual increase. These changes are, however, comparatively 
small. 


The Position and Nature of Liquid Water. 

It is very remarkable that, in accord with its simple formula, 
water should stand at the head of the symmetrical ether series— 
and is, in fact, its vanishing point. 

In this it is analogous to hydrogen (H a ) which is the vanish¬ 
ing point of the hydrocarbon series. In contrast to unsymmetri- 


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no 


LIQUID CHEMICAL COMPOUNDS. 


cal methyl alcohol, water is a symmetrical compound, and there 
is a corresponding difference in the volumes of O in the two 
compounds. 


H—o—H 
CH S —O—CH 3 
The symmetrical ether 
series. 


- H, 

CH 3 —O—H CH 4 

The alcohol The paraffin 

series. series. 


The formula apparently indicates the existence of a hydroxyl 
group, but it is more in accord with the formulae for the sym¬ 
metrical ethers. 

As regards its volume, which is 187, we may suppose that it 
is made up as follows:— 

[H 2 0 ] = 2[H] + [O] = 2 x 37 + n*3 = 187. 

The volume of oxygen ^>0 is thus 11 3. 

This is considerably larger than that of hydroxyl oxygen as 
found in the alcohols. 

[C 6 H 13 OH] = [QHjJ + [O] = 139-9 + 6-5 = 146-4. 

The volume of O' is thus 6*5, a number which is quite 
different from its former value. The volume of oxygen in water, 
however, agrees with the idea that on the whole it is ethereal in 
character. An examination of dimethyl ether shows this. 

[(CH 3 ) a O] - 2[CH 3 -] + [> 0 ] = 52-0 + 107 = 62-7. 

This value 107 is not very different from that obtained from an 
examination of water. 

These calculations show that water is not a hydroxyl com¬ 
pound, but one of the symmetrical ethers. 

It has been known for some time that the simple formula 
H 2 0 , whilst doubtless representing one particular type of mole¬ 
cule, does not express the nature of water as a whole. Liquid 
water is an associated substance, that is, it is made up of mole¬ 
cules which are polymers of H 2 0 . Its formula might be ex¬ 
pressed by (H 2 0 )at, where x is a number which is greater than 
unity. It is, moreover, known that the value of x cannot be 
expressed by a simple number, but water is a complex of many 
types of molecule. 

Armstrong 89 has endeavoured to show that these fall into two 
classes. 


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ORGANIC COMPOUNDS CONTAINING OXYGEN. hi 


(a) Those which are similar in configuration to the paraffin or 
open-chain series —in fact to the normal alcohols. 


H 

H 

/ 

h 2 o h 


/ 

\/ 


h 2 o 

0 H 

etc. 

\ 

/\/ 


OH 

H 0 


or 0 H 3 —OH 

OHg— 0 H 2 —OH 

which are similar to 

CHg—OH 

CH 3 —CH 2 —OH 

and so on. 

(U) The hydrones which 

are similar to ethylene and the poly ■ 

methylenes . 

H, 

H a H 2 

H 2 0 « 0 H 2 

6 

6—6 

/\ 

1 1 


H a . O O . H, 

0—0 

Dihydrone. 

Trihydrone. 

H„ H a 

Tetrahydrone. 


h 2 

h 2 h 2 

CH 3 = ch 2 

c 

C—C 


/\ 

1 1 


H a . c — c . h 2 

c—c 

Dimethylene. 

Trimethylene. 

H a H, 

T etramethylene. 


These formulae are consequent upon the assumption of 
quadrivalent functions by oxygen. 

It may be shown, by means of molecular volumes, how far 
this hypothesis is justified at the boiling-point. 

We do not know the volume of quadrivalent oxygen ex¬ 
cept as indicated by the single compound hydrogen-dioxide 
H- 0 = 0 - H. 


The volume of - O = is found to be 8*o. 

Since, with the exception of water, all of the above formulae 
involve quadrivalent oxygen, the average volume cannot be 
greater than 15*4, if we consider compounds of class (a) alone 
and of complexity higher than (H 2 0 ) 2 . 

On the other hand, if we consider the influence of the 
hydrones, we come to the conclusion that the average volume 
would be considerably less if these existed in any large proportion, 
because ring compounds are subject to considerable contractions. 


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I I 2 


LIQUID CHEMICAL COMPOUNDS . 


We are thus left with the simple molecule H s O and the more 
complex ones, OH 2 = OH 2 and OH 8 - OH. 

The volume of OH 2 = OH 2 would be 35-5, comparing it with 
ethylene. This gives an average value of 17*7. 

The volume of OH 8 . OH would be 36*2, or an average of 
18-1 for H 2 0 . 

If, however, we remember that the tendency of H is to increase 
the volumes of the simple compounds in which it occurs, as for 
example in CH 4 , QH^, HC 1 and the initial members of most 
series, the volume of simple H a O at the boiling-point might be 
20 0 or even more. 

On the whole, we think that at the boiling-point liquid water 
might consist mainly of 

H a O, OH 8 . OH and OH 2 = OH 2 

with perhaps smaller proportions of compounds of complexity 
(H 2 0 ) 3 . It is not, however, probable that the other more com¬ 
plex compounds could occur, especially those which involve ring 
structure. 

In accord with this we find that most physical properties 
show an association factor of between 2 and 3. 


Physical Property. 

Association Factor. 

Capillarity (Ramsay and Shields) 

26 

Mol. Cohesion (Walden) 

1*98 

Volume (Traube) .... 

30 

Fluidity (Bingham) .... 

2*2 

Mean 

2*4 


Certain other ethereal compounds are interesting. 


Ethidene dimethyl ether C 2 H 4 (OCH 8 ) 2 


CH 8 . CH 


/OCH 8 

\ 0 CH, 


V m = 

(CH,) a CH . CH, 
V* 


II 2'3 

96*5 

II 2’3 


2[0] = 157 
[> 0 ] - 7-85 


This volume of the above ethereal oxygen is similar to what 
we find in QH,—O—CH 3 , but considerably less than in 
C S H S —O—CH a . 


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ORGANIC COMPOUNDS CONTAINING OXYGEN 113 


ether C 2 H 4 (OC 2 H 5 ) 2 

Vm = 160*2 
(C 2 H 6 ) 3 CH . CH S 139-0 

C 2 H 4 . (OC 2 H b ) 2 160*2 

2 >0 21*2 

>0 10*6 

The volume of the ethereal oxygen is similar to what we find 
in C tf H 5 — 0 —C 2 H 6 , and is more in accord with the number 
found in ethers of the type R—O—R'. 

The above compounds thus show agreement with the ethers 
of the monohydric alcohols, in that the methyl group causes a 
depression in volume as compared with the volume when the 
ethyl group is present. 

The explanation of the particular value found is not quite 
easy. The molecules are of the branched chain type of structure, 
the effect of which in this class of compound has not been studied 
sufficiently. In compounds with a single —OCH 8 group, the 
depression is (io*6 - 9 6) ro, as compared with compounds with 
those having a single —OC 2 H 5 group. 

In those with two —OCH 3 groups, the total depression is 
2 (io-6 - 7-85) = 2 x 275. On the whole, there is an outstanding 
difference of 3*50. 

The Effect of the Addition of the Homologous Increment 
CH 2 on the Volumes of the Ethers. 

The aliphatic ethers (see Dobriner, ref. 17) may be divided 
into series, e.g. that of the methyl ethers CH 8 —O—CH 8 , the 
ethyl ethers C 2 H 5 —O—C 2 H 5 , etc., each of which symmetrical 
compounds stands at the head of a series. The methyl CH 8 , 
ethyl C 2 H 5 , etc., groups will appear on one side throughout the 
series, a radicle of variable complexity appearing on the other side. 

It has been shown that the volumes of the ethers and those 
of certain esters are nearly the same, and that both series may be 
represented by a similar number of hydrogen equivalents W. 

The ethers C»H 2n + 2O show values of W which are equal to 
6 n + 5, because [> 0 ] = [3H] and [C] = 4 [H]. 

The esters C»H 2w O also show values of W equal to 6 n + 5, 
because O' = 2H and O' = 3H. 

If we know the molecular volume of a compound and the 

8 


Ethidene diethyl 
OC 2 H 5 


CH„. CH/ 

\oc 3 h 5 


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Values of v /w 


LIQUID CHEMICAL COMPOUNDS. 


114 

number of hydrogen equivalents, the ratio V/W gives the volume 
of a single hydrogen equivalent This enables us to find the 
variation in the volumes of H, and thus of every atom, throughout 
the homologous series. 

TABLE LIII. —The Aliphatic Ethers. 





R—1 

0—R'. 





The Dimethyl series. 



The Diethyl series. 


w. 

Compound. 

V m . 

V/W. 

W. 

Compound. 

Vm. 

v/w. 

17 

CHj—O—CHo 

62*6 

3*680 

29 

c 2 h 5 —0—c 8 h 5 

106*2 

3-664 

23 

CHj—O—C 2 H b 

84*2 

3*660 

35 

c 9 h 5 —0—c 8 h 7 

128*1 

3-659 

29 

CHj—O—C 8 H 7 

105*1 

3*624 

4i 

c 2 h 6 —0—c 4 h 9 

150*3 

3-666 

35 

CHj—O—C 4 H 9 

127*5 

3*643 


— 

— 

— 


_ 

_ 

__ 

59 

c 9 h b —0—c 7 h 16 

221*3 

3751 

53 

CHj—O—C 7 H 15 

195*0 

3*680 

63 

c 9 h 6 — 0—C 8 H 17 

247*2 

3-803 

59 

CHj—O—C 8 H 17 

220*2 

3*732 






Dipropyl series. 



Dibutyl series. 


W. 

Compound. 

M.V. 

V/W. 

W. 

Compound. 

M.V. 

V/W. 

4i 

CjHt-O-CjH, 

151*3 

3*689 

53 

C 4 H 9 —0—C 4 H 9 

197*7 

3-728 

47 

CjHt-O-C.H, 

173*2 

3*686 


— 

— 

— 


_ 

_ 

_ 

7i 

c 4 h 9 —0—c 7 h 15 

272*0 

3-831 

65 

C s H 7 —O—C 7 H 15 246*1 

3786 

77 

C 4 H 9 —0—C 8 H 17 

297*4 

3-862 

7i 

^8^7-O-C 8 Hj 7 273*0 

3-845 







20 30 40 50 60 70 80 

Number oP H Equivalents. 


Fig. 3* 


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ORGANIC COMPOUNDS CONTAINING OXYGEN 115 


The above calculations show that, except at the beginning 
of series, there is a general increase in the value of V/W. 
Normally it should eventually be abouj 0*30 for each addition 
of CH 2 . There are signs that this is the case, if we depend 
on the evidence of those series which do not include C 7 H 15 or 

c 8 h 17 . 

The differences in the latter cases are over 0 50, which is 
double to that ordinarily found. This makes the slope of the 
curves for these complex compounds steeper than usual, e.g. 
as shown by the line C 38 C 37 , etc., in the diagram. 

There is thus an apparent absence of continuity in the values 
of V/W between the simple and the more complex compounds. 
An examination of the C 5 H n and C c H 13 ethers would show 
whether this is real or not, and in the latter case, how the two are 
connected. An attempt has been made to show this connection 
in the curve for the ethyl ethers C 22 . . . C 28 . Excluding the 
methyl ether curve, which is different from the others, the curve 
just mentioned probably resembles in form those for other series 
as e.g. the normal paraffin series. 

Thus, we find a nearly horizontal portion like ^ 22 ^ 23^24 which 
includes a minimum. This minimum is very pronounced in the 
methyl ether curve, is still apparent in the next succeeding, 
and then practically disappears in the others. 

Subsequently, we find an ascending portion which appar¬ 
ently is partly coincident with the ascending portion of the 
methyl ether curve C 14 . . . C 18 . This finally leaves the straight 
line, and the slope becomes steeper, as shown by the parts 
^ 27 ^ 28 * C 37 C 38 . 

A remarkable fact, however, is, that the compound C 17 , instead 
of finding its position on the line at a point marked O, is situated 
considerably below this, viz. V/W 3708 - 3*680 = 0*28. If, 
however, we join the points C 17 and C 18 , we get a line which 
is parallel with the steeper portions of the heptyl and octyl 
curves, although C 17 is out of position. This is all the more 
remarkable. 

It follows from the fact that the gradients of C 27 C 28 , and 
C 87 C 38 are much steeper than has been found usual, and also that 
C17C18 has a similar gradient, although C l7 is out of position, that 
the molecular volumes of these and perhaps other compounds, are 
liable to vary from the expected values, from causes at present 

8 * 


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n6 


LIQUID CHEMICAL COMPOUNDS, 


unknown. These variations, however, do not seem to be due to 
experimental errors, nor to the existence of small quantities 
of accidental impurities. The whole question of the causes of 
the divergences of molecular volumes from those expected, 
and the causes of variation in the values given by various 
observers, is a difficult question, but well worth study. It is 
probable that unlooked for features might be discovered, either 
as applying to the molecules themselves, or to the characteristics 
of liquids. 

The Symmetrical and Unsymmetrical Ethers. 

Ignoring the divergent values, and depending on the principle 
of continuity, we obtain the following curves shown in the 
diagram (Fig. 4). 

I, The curve for the symmetrical compounds, 

II, The curve for the unsymmetrical compounds, 

III, The curve for the methyl series, 

I. and II. are similar in form , which would lead us to conclude 
that the form is dependent on complexity , or the number of C 
atoms in the chain, and not on their character, symmetrical or 
otherwise. 

Their position is, however, dependent on the relative number of 
C atoms on each side of the typical oxygen atom i.e. on 
the degree of symmetry. 

Curve I. represents compounds of type An = o, or the 
perfectly symmetrical. 

Curve II. represents compounds of type An = 1, or com¬ 
pounds less symmetrical by one C atom. 

This difference of one C in the radicles on either side of O is 
shown by a displacement of the curve in, say, the direction of 
increasing complexity, that is, there is a relative decrease in the 
value of V/W for want of symmetry. 

In the case of the simpler compounds, an additional divergence 
from perfect symmetry is shown by an additional diminution in 
volume, but higher up this apparently vanishes, the compounds 
diverging more than An = 1 from perfect symmetry, are nearly, if 
not entirely, of the same volume as those for which An = 1 
is true. 


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ORGANIC COMPOUNDS CONTAINING OXYGEN . 117 


It is to be observed that the most symmetrical compounds, 
that is, those which stand at the head of each series, possess con¬ 
siderably larger volumes than those which might be expected. 
This gives that peculiar feature to the curves which may be 
observed from an inspection of the diagram, namely, that portion 
which occurs before the minimum, and which is marked by 
decreasing values of V/W. Since this characteristic also applies 
to the paraffin series, and as a matter of fact to all series, we see 
the analogy of these more symmetrical compounds with the first 
members of the other series. Dimethyl oxide is, for instance, a 
symmetrical compound, but it is also the first member of the 
methyl ether series, and corresponds to methane, methyl alcohol, 
methyl bromide. It seems to follow that the particular feature 
of symmetry, which is a characteristic of dimethyl ether, is that 
which also distinguishes the initial members of the other series, 
and which influences their volumes. Whether the cause be 
simple or complex, as indeed is probable, the operating influence 
is no doubt the general shape of the molecule and possibly 
its complexity or length of chain. For the present, limiting 
our view to the ether series, we distinguish two classes of com¬ 
pounds— 

{a) the symmetrical ; 
and {b) the less symmetrical , 

that is, we have to distinguish those in which R- R' = 0 from 
those in which R-R' = CH 2 . The special feature applying to 
the latter is apparently confined to the ether series and is ad¬ 
ditional to that which may apply to the compounds R- R' = 0 , 
as distinguished from those marked by the characteristic 
R - R' = «CH 2 , and which includes all the members of the series 
which are less symmetrical than the absolutely symmetrical com¬ 
pounds. 

Certain well marked diminutions are noticed in the com¬ 
pounds which are most unsymmetrical, i.e. those which contain a 
single methyl group, and sometimes, but to a lesser extent, 
those containing an ethyl and even propyl group. Whether this 
diminution is due to non-symmetry simply, or to the special 
influence of the CH 8 , C 2 H 5 , etc., groups, is a very difficult ques¬ 
tion to answer, and indeed is that one which presses most. 


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Values oF yto 


118 


LIQUID CHEMICAL COMPOUNDS. 


TABLE LIV.— The Aliphatic Ethers. 


R—O—R'. 


Symmetrical. 

R—R' = 0 . 

W. Compound. V w . V/W. 

17 CH 3 —O—CH 3 626 3680 

29 C 3 H 5 —O—C 2 H 5 106*2 3*664 

41 C 3 H 7 —O—C 8 H 7 151*3 3*689 

53 C 4 H 9 - 0 -C 4 H 9 197*6 3*728 

65 QH11—O—C 5 H u — — 

77 C 8 H X3 O C 6 H 13 

89 C 7 H 15 —O—C 7 H 16 353 42 3*971 


Unsymmetrical. 

R—R' = CH a . 

W. Compound. V m . V/W. 
23 CH 3 —O—C 4 H 5 84*2 3*660 
35 C a H 5 —O—C 3 H 7 1281 3*659 
47 C 3 H 7 —O—C 4 H 9 173*2 3*686 
59 C 4 H 9 —O—C 6 H n — “~ 

71 C 6 H X1 —O—C g H 13 — 

83 C 6 H 13 —O—C 7 H 15 — — 

95 C 7 H X5 - 0 -C 8 H 17 377*6 3*975 



Number of H Equivalents 

Fig. 4. 


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ORGANIC COMPOUNDS CONTAINING OXYGEN 119 


Formula Representing the Results for Complexity and 
Symmetry in the Ethers. See Le Bas, Ref. 40 

An attempt has been made to represent the above results by 
a formula. 

It has been shown that for the n paraffin and other series, the 
formula 

v m = W{S + (W - 4 o)K } 
reproduces the results— 

W indicating the number of H equivalents; 

S the least or minimum volume of H in the series; 

K a number indicating the variation in volume of one H equivalent for an 
addition of one H or its equivalent. 

The above-mentioned curves require a more complex formula 
to indicate them. 

I. The effect of complexity is proportional to the cube of the 
number of C atoms. 

Al = 0r~ 2 ) (l~ I ) x 00101 

and 

II. The effect of want of symmetry is proportional to the 
square of the number of C atoms, the symbol n representing 
their number. 

As = n 0 x 0-003. 

The whole formula is— 

M.V. = (6» + 5) {3-664 + - 2 ) (j - *) * o-oio - » 0 x 0-030} 

W = 6n + 5 S = 3*664. 


TABLE LV. —Calculation of the Volumes of the Symmetrical and 
Unsymmetrical Ethers by Means of Formula. 


Class. 

Compounds. 

w. 

n . 

V/W. 

Corr. 

for 

unsymm. 

v/w 

calc. 

V/W 

obs. 

V calc. 

V obs. 

S 

CH S . 

0 . 

CHo 

17 

2 

3664 



3-677 

62-25 

62-5 

U 

CH„. 

0. 

C,H» 

23 

3 

3-661 

- o-oog 

3-652 

3-652 

84-00 

84-0 

S 

C 2 H b 

0 

C,H S 

29 

4 

3-664 


3-664 

3-664 

106-25 

106*2 

U 


0 

C»H, 

35 

5 

3-67* 

- 0-015 

3-657 

3-659 

128*00 

128*08 

S 

c,h 7 . 

0 

c,h 7 


6 

3-684 


3-684 

3-689 

151-04 

151-27 

u 

c,h 7 . 

0 

• c 4 h„ 

47 

7 

3705 

-0*021 

3-684 

3-686 

173*15 

173*25 

s 

£H,. 

0 


53 

8 

3725 


3-725 

3-73o 

197*42 

197*72 

u 

L> 4 H 9 

0 

C 8 H n 

59 

9 

3752 

- 0-027 

3-725 

3-733 

219*77 

22035 

s 

C.H U 

.0 

•C,H U 

65 

10 

3785 


3-785 

3-789 

246*02 

246*28 

u 

C»H U 

.0 

c*h m 

7i 

11 

3*823 

-0-033 

3*790 

3-795 

269*09 

269-44 

s 

C,Hj, 

.0 

• C,H 1S 

77 

12 

3-866 


3-866 

3-867 

297*68 

297-76 

u 

c 7 h„ 

.0 

■C,H U 

83 

13 

3*9i4 

-0-039 

3-875 

3-870 

321-62 

321*21 

s 

C,H„ 

.0 

■ c 7 h u 

89 

14 

3-967 


3-967 

3-970 

353-06 

353*42 

u 

c 8 h 17 

.0 

• c 7 h„ 

95 

15 

4*025 


3-980 

3-975 

378-1 

377-6 


The compound (C 8 H 7 ) 2 0 is not given as its volume does not conform to the 
rule just given. Young 41 has, however, shown that the b.p. for this compound is 
too low. Given a higher number, there would probably be coincidence between the 
calculated and theoretical values. 


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120 


LIQUID CHEMICAL COMPOUNDS . 


In studying the compounds of the methyl series, either by 
means of Table LIII., or better from Fig. 3, we see the effect 
of a CH 3 group on the volume of a compound 

R—O—CHg 

is, generally, to depress the volume. This is so at least down 
to the compound in which R = C 3 H 7 , but as R becomes less 
complex, the effect is an augmentation of V/W. 



V/W 

CH 8 . CH a . CH 2 .0 . CH 8 

3*624 

ch 8 . ch 2 .0. ch 8 

3’66o 

CH 8 . O . CH 8 

3680 


This result may be ascribed to a number of causes : (a) 
diminishing complexity, (b) increase of symmetry, (c) increase in 
the compactness of the molecule. Probably all of these influences 
contribute to the result, but they are not independent, and thus 
the analysis cannot be made. 

An Examination of the Various Constitutive Effects 
Associated with Hydrocarbon Chains. 

In the following attempt to analyse the conditions which 
give to the molecular volumes of the ethers their particular 
character, it might seem that we look upon the factors as being 
independent one of the other. In reality, it is probable that 
they are not independent , so that real analysis is difficult, if not 
impossible. Still our view of things may not be without its 
advantages and of some interest. 

The influences operating on hydrocarbon chains are:— 

(a) Complexity with which may be included length of chain. 

The effect of this is probably always to augment the atomic 

volume. By complexity we do not necessarily mean increase in 
the number of atoms, still less, and increase in the molecular 
weight, but rather increase in the number of units of volume 
(see Fig. 5). 

This is, in normal chains, complicated by a second factor. 

(b) One which is closely related to compactness of molecular 
form . 

This is a maximum for the first member of each series—the 
methyl compound. 

If we take the carbon atom as a centre, it is possible, by 
assuming that the shape of methane is a regular tetrahedron, to 


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ORGANIC COMPOUNDS CONTAINING OXYGEN. 121 


describe a sphere about this centre so as to include all the H 
atoms. These H atoms would be situated on the surface of the 
sphere. 

In the case of ethane and propane , etc., the corresponding 
figures would be gradually elongating ellipsoids of revolution. 

Plane projection would show them as circles and ellipses. 

This compactness, or rather diminishing compactness, tends 
to diminish the atomic volume, but the observable influence of 
this factor, extends to only the fourth or fifth member of each 
series. At this point the influence of increasing complexity 
becomes predominant. 


The Influence of Compactness of Molecules. 

Unbroken C Chains. 

Homogeneous Attachments. 

The n Paraffin Series. 


f T \ f 

(h— c— h] 


1 

H 


v/w 4 - 8.5 
No. of atoms 1 
in molecular 
chain. 


H 

H— A— OH 

k 

V/W 4-28 
No. of 1 
atoms in 
chain. 



H H H h\ 

I I I I \ 

-O^O-O-O-H] 
1111 / 
H H H H / 


Unbroken Chains. 
Heterogeneous Attachments. 

The Alcohol Series. OH = 3 V/W. 


H H 

H H H 

H H H H 

-A— C—OH 

I I 

1 1 1 

H—C—C—C-OH 

1 1 1 

1 1 1 1 

H—C—C—C—C—OH 
l l 1 1 

H H 

H H H 

1 1 1 1 

H H H H 

3*88 

3*70 

3*647 

2 

3 

4 


V/W 
No. of 1 
atoms in 
chain. 



The Chloride Series. Cl = 6 V/W. 


H 

H H 

H H H 

H H H H 

H—t—Cl 

H—A—(t—Cl 

H—i—A—i—Cl H- 

—i—(1 —C—t 

A 

A A 

A U 

u u 

3-90? 

3774 

3-668 

3-661 


Cl 


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122 


LIQUID CHEMICAL COMPOUNDS . 


The Bromide Series . Br = 7*5 V/W. 


H 

H H HHH 

H H H H 

H—C—Br 

H— i—i— Br H—t— i —d—Br 

H— A—A—<L- i— Br 

k 

U iik 

u u 

V/W 3-84 

3780 3*672 

3'®49 

No. of atoms 1 
in chain. 

2 3 

The Iodide Series. I = 10 V/W. 

4 

H 

1 

H H HHH 

H H H H 
H—i—C— L —C—I 

H—C—I 

1 

II III 

H—C—C—I H—C—C—C—I 

11 111 

1 

H 

II J 

H H HHH 

a i. a 

V/W 3*770 

3730 3*683 

3*663 

No. of atoms 1 

in chain. 

2 3 

Broken Carbon Chains . 

The Ethers. 

4 

H 

H HHH 

HHH H 


V/W 

No. of atoms 
in chain. 


V/W 

No. of atoms 
in chain. 


H—i—O—A—H H—C—C—0—C—H H—i—i—i—o—i—H 

t i H i kkk i 

3*680 3*660 3*628 

3 4 5 

HH HH HHH HH 

H _u —O— u —H H—i—it— o —i—C—H 

u u ha a 

3*664 3*659 

5 6 


In the above-mentioned compounds the influence at work 
is, as it were, a mutual repulsion between the atoms attached to 
the same C atom. 

Such a mutual repulsion is exerted by H, Cl, Br and I atoms 
among themselves, and the effect is a maximum when all the 
atoms attached to the carbon are of the same kind (see p. 12 5). 

The rule, which may be applied to the different series, is, 
that the volume tends to a maximum in a series , as the shape of 
the molecule becomes most compact , i.e. when it may be enveloped 
by a sphere of revolution . This will naturally be the simplest 
member. 

When there is reason to believe that mutual attractions are 


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ORGANIC COMPOUNDS CONTAINING OXYGEN 123 


possible, the above rule is no longer true. The effect indeed is 
exactly the opposite of the above. An example of this is found 
among the branched-chain hydrocarbons. The rule is 

That the volume tends to a minimum , as the shape of the mole - 
cule approximates to that of the sphere . 

An example of this attracting influence between groups is 


Tetramethyl methane. 

Di-isopropyl. 

CH, 

ch 3 ch 3 
11 

CH,—C—CH, 

1 1 

H—C-C—H 

1 | 

CH, 

1 1 
ch 3 ch s 


We-should be inclined to attribute the expanding effect to 
the influence of the attached atoms H, Cl, Br, etc., but the con¬ 
tracting effect to a residual action of the intense self-affinity 
which characterizes carbon, and which persists in spite of the 
presence of the other atoms. 

Closely associated with the above influence is a third— 

(c) The homogeneity or heterogeneity of the attached atoms . 

In studying the methyl and ethyl compounds belonging to 
the various series, we notice that when an atom or group other 
than hydrogen takes the place of hydrogen, the atomic volumes 
become smaller. 

The amount of the diminution increases as the volume of the 
heterogeneous atom increases. 

The diagram on next page better illustrates this. 

The two curves—that for the methyl and ethyl compounds 
respectively, are very similar. 

In both, we see that the volumes of the atoms diminish with 
an increase in volume of the heterogeneous atom attached to 
carbon. 

Homogeneity then tends to expand the volumes, and hetero¬ 
geneity to contract them. 

This is well shown in the following— 


H 

H 

1 

H 

1 

Cl 

1 

Cl 

| 

H—C—H 

1 

H—C—Cl 

1 

H—C—Cl 

1 

H—C—Cl 

1 

Cl—C—Cl 

1 

A 

1 

H 

1 

Cl 

Ai 

Cl 

4*85 

3*88 

3*617 

3*674 

3704 


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LIQUID CHEMICAL COMPOUNDS. 



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ORGANIC COMPOUNDS CONTAINING OXYGEN 125 


and also in the corresponding bromine compounds— 

H H H Br Br 

—H H—C—Br H— C—Bt H—i—Br Br—i- 


H- 


A 


Br 


V/W 4-85 


H 

384 


A, L 


3'895 


3 ’ 7®4 


A, 

probably higher. 


It will be noticed that there is an increase in complexity as 
well as a change in homogeneity as we proceed from left to right. 
It is difficult to consider them apart . The above values find their 
place on a curve similar in character to the curves for the 
normal series. The homologous increments in these cases are 
—[H] + [Cl] and —[H] + [Br]. 

The effect due to homogeneity is much greater when the 
volatile hydrogen is present, than when replaced by the heavy 
chlorine atom. 

In compounds like 


Cl 


Cl—Sn—Cl 

b 


Br 

Br—Hg—Br < lb—Br 

Ir 


the halogen atoms possess their maximum values. 


Exception. 


Br 


< 


u 

ir 


Cl aa 22*2 Br 28*0 or over. 


In this case, the atomic volumes of Br are 
27*0, similar in fact to that of P, instead of 28 or 
more. 


Heterogeneity on the other hand usually results in a diminu¬ 
tion of the volume. 

This has been shown to be the case in 


CHgClg CHClj, CH s Br a 
Cl 


Br—L—Cl 

A 

Cl 

NO a —( 1 —Cl Vm 110*9 

ii 


V m 108*4 CCIj 81*4 Br 27*0 


CO,, 81*4 NO a 29*5 

Normal 32*0 


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126 


LIQUID CHEMICAL COMPOUNDS . 


Thus the effect of homogeneity is an apparent repulsion 
between the atoms attached to the central atom, and the effect of 
heterogeneity is an attraction. These influences respectively pro¬ 
duce expansions and contractions. 

The following cases are also interesting:— 


Cl 

0 = 1 *—Br V w = 107*4 


P 0 C 1 , 79-4 

| 

Br 28*0 

Cl 

S»Va 107*4 


Vm 107*4 

which corresponds to 

Cl H # 

Cl—d—d Vm = 1067 

i 11 

Cl 0 


CC 1 , 81*1 
CHO 25*9 


2 nVa 107*0 


Vm 1067 


The atom : O does not seem to be able to act in a manner 
similar to that of the monatomic elements with single linkings or 
with groups like N 0 2 singly linked. 

It should be remarked that whereas chlorine atoms attached 
to the same carbon atom give rise to expansions , or, perhaps, more 
accurately, allow the volumes of the atoms to attain their full 
value, on the contrary, when they are attached to different 
carbon atoms, they cause contractions . This is an additional 
feature which has already been noticed. 

(i) Symmetry . The effect of this has also already been in¬ 
vestigated, at any rate in the case of the ethers. 

Thus in the compounds C # H 14 0 and C 6 H 12 0 we find the 
following characteristics. 


H H 


H H H 


„-U- O— LU — H 

Li LLi 

v/w 3-659 


H 


H H H H 


H— d —o—c—c—c— i: —h 

i mi 


3-643 


H H 

I 


H 


H H H 
H. —*.** . ... •••!..—1 —C - 

LLL LLi 


-H H- 


V/W 


3*689 


H H 

.u^ 

u 


H H H H 

_u 

u 

3*666 


-U 


H H 


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ORGANIC COMPOUNDS CONTAINING OXYGEN 127 


In both of the above instances the complexity is the same, 
as also the degree of compactness of the molecule, but the degree 
of symmetry or distribution of carbon atoms about the oxygen 
atom is different. 

The most symmetrical compound possesses the largest volume, 
and the values of V/W diminish as the degree of symmetry 
becomes less. 

In the ethers at any rate, degree of complexity modifies the 
effect of symmetry, or rather want of it. Thus the effect of want 
of complete symmetry among the higher compounds is not nearly 
so marked as among compounds lower down in the series. 

The effect of degree of symmetry on the volumes of the 
atoms, and thus on the molecular volumes, is best shown by 
some of the esters of the monocarboxylic acids. 


TABLE LVI.— Isomeric Esters. 



C 7 H 14 O a 


M.V. 

B.P. 

C,H„ 

. CO 

. 0 

. CH, 

172*2 

149*6 

C 4 H,. 

,CO. 

0. 

C,H, 


144*6 

c # h 7 , 

. CO . 

0. 

c,h 7 

174*0 

i 43 *o 

C t H,. 

. CO . 

0 . 

c 4 h. 

146*0 

CH,. 

CO . 

0. 

CjHjj 


148*0 

H.CO . O 

.c ( 

.H u 

173*3 

153*2 


C 8 H w 0 2 M.V. B.P. 

C 6 H X8 . CO . O . CH 8 196*2 173*0 

C 5 H n . CO . O . C 2 H 5 197*7 167*0 

C 4 H 9 . CO . O . C 8 H 7 197*8 167*0 

C 8 H 7 . CO . O . C 4 H 9 197*8 165*7 

C,H 6 . CO . O . C 5 H n 
CH 8 . CO . O . C 6 H 13 197*7 i6 9‘° 

H . CO . O . C 7 H 15 196*7 176*0 


We see that the most symmetrical compound possesses the 
largest volume and the lowest boiling-point, whilst, on the other 
hand, the least symmetrical compound possesses the smallest 
volume and the highest boiling-point. 

In the above series, as distinct from that of the ethers, the 
least symmetrical compounds are at the beginning and ends of 
the series, and the most symmetrical compounds are situated 
near the middle . 


In molecular volumes there is thus a rule analogous to that 
stated by Hinrichs, 42 1868, for the boiling-point, which is, that the 
more symmetrical the formula of an isomeric molecule is the lower is 
the boiling-point This is similar to Naumann’s statement of it 
(1874). The effect on volume is of the nature of an expansion. 


The Phenolic and Other Ethers. 

The group —O—R can be attached to a radicle of the type 
C # H 5 - as well as to an aliphatic radicle R'. 

R'—O—R C 8 H b —O—R 

Aliphatic ether. Phenolic ether. 


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128 


LIQUID CHEMICAL COMPOUNDS ,. 


The phenols and similar compounds have already been 
studied, and it has been shown that there is a contraction of 0*8 
as compared with the alcohols, when the methyl group is present. 


TABLE LVII.— Phenolic Ethers . 48 

V w . 


Phenol methyl ether anisol 
Toluene 

C 6 H 8 . O . CH, 
C e H 5 . CH, 

125*5) 

Il8*2j 

O' 

7*3 

Phenetol 

Ethyl benzene 

C 8 H 8 . O . C,H„ 
C c H 6 . c,h. 

149-31 
139-3 J 

t °' 

io-o 

Phenyl propyl oxide 

Propyl benzene 

c„h 8 .0. c,h 7 
c.h 8 . C 3 H 7 

172-41 
162-2 J 

t °' 

io-o 

Phenyl butyl oxide 

Butyl benzene 

c 8 h 8 .0. c 4 h, 
c 8 h 5 . c 4 h. 

195*7) 

184-5 j 

0 ' 

11*2 


TABLE LVIII.— Cresylic Ethers. 

V*. 


p Cresyl methyl oxide 
p Xylene 

C,H 4 (CH 8 ). 0. CH, 
C„H 4 (CH,), 

147-61 

140-51 


O' 

7*i 

p Cresyl ethyl oxide 
p Ethyl toluene 

C,H 4 (CH,) . 0 . c,h 8 
C«H 4 (CH,). CjH, 

H W 

ff'S 

oJ Ur 


O' 

10*2 

p Cresyl propyl oxide 
p Propyl toluene 

C 8 H 4 (CH,) . 0 . c,h 7 
C„H 4 (CH s ) . c,h 7 

196-51 

184-9 j 


O' 

ii*6 

In comparing the 

aliphatic and aromatic ethers, 

in 

respect of 


the volume of O', we notice that it is only the methyl compounds 
which differ, 9"6 and 7 2 respectively. When the groups are more 
complex, there is very little difference between the volumes of O'. 

A Study of the More Complex Aromatic Ethers. 

The more complex ethers possess additional expansions owing 
to their increase in complexity. 

Thus 

Phenyl heptyl oxide C a H„—O—C 7 H 16 V m = 271-4 

C,H 6 928 

O" io*o 

C,H„ 158-9 

2»V a 261-7 

Observed 271-4 

A = + 97 3 * 3-2 (Cr-Ci) 

Phenyl octyl oxide C 8 H^—O—C 8 H 18 Vm = 296*8 

C 6 H s 92-8 

O" io*o 

C 8 H 17 i8ro 

2«V« 283-8 

Observed 296-3 

A = + 12-5 4 x 3-15 (C 8 —CJ 


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ORGANIC COMPOUNDS CONTAINING OXYGEN 129 


A slight increase is noticed at —O—C 4 H 9 , but after this there 
is an increase of 3*2 for every addition of CH 2 . 

The Thymols, 

Methyl thymol C 8 H 7 . C 6 H 8 . (CH 8 )OCH 8 Vm = 214-8 * 

Cymene C 8 H 7 . C 6 H 4 . CH S 184-7 

less H 3-2 

181-5 
O' 7-4 

CH, 25-5 

214-4 
V m 214*8 


Ethyl thymol C 8 H 7 . C 6 H 8 (CH 3 )OC*H 5 V m = 240-5 
Cymene C 10 H 14 less H 181-5 

CjH b 48*0 

O' ii-o 

2nV a 2405 

V m 240-5 

C 6 H 4 89-6 

O' 5-6 

C 8 H 7 70-0 

CH 8 255 

5nVa 190-7 

V m 189-3 

-1-4 for 0 structure. 

This is all the more remarkable seeing that the ortho cresylic ethers show it. 

It follows from the above calculations that 

—O—CH S gives a value of O' equal to 7-4 
ZoUr* 1 * 6 an< * } 8* ves values of O' equal to 10-n. 

When the total value of the side chains equals C 4 or C 6 there 
is a large increase in the volumes. This is due to complexity 
and involves every atom in the compound. 

Since the volume of—OCH 3 is the same in aliphatic methyl 
esters, and in aromatic methyl ethers, we are inclined to connect 
the contraction with the presence of unsaturation. Note the 
following:— 

♦None of the thymol ethers show any contraction for ortho structure (vide 
infra). Compare thymol itself (q.v.) 

9 


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130 


LIQUID CHEMICAL COMPOUNDS. 
o=c— 

Jc 


iCH a 


c=c< 

OCHg 
/OCHg 
— CH' 

\0CHg 

in all of which >0 = 7—8, and compare with this R—O—CH 3 
in which >0 = 9*6. The conclusion before arrived at, seems the 
only one possible. 

The Cresylic Ethers. 

p Cresyl butyl oxide C 6 H 4 (CH S )0 . C 4 H 9 Vm = 221*3 


C 

-CH, 

c 6 h 4 

8g*6 

/ ' 

\ 

CHg 

25*5 

CH 

CH 

O" 

10*0 

| 

|| 

C 4 H 9 

92*3 

CH 

CH 

2«Va 

Vm 


\ . 

C 

/ 

—0—C 4 H„ 

217*4 

221*3 


A = + 3*9 ix 3*9(C 6 -C 4 ) 

p Cresyl octyl oxide C 6 H 4 (CH 3 ). OC 8 H 17 V m = 323*1 


C-CH, 

c,h 4 

8g*6 

s \ 

CH, 

25*5 

CH CH 

1 II 

0" 

10*0 

C 8 H„ 

181*0 

CH CH - 

\ / 

2»Va 

306*1 

C—0—C.H,, 

Vm 

323*1 


A = + 17*0 5 x 3*4 (C 9 - C 4 ) 

The Thymols. 

Propyl thymol C 3 H 7 . C 6 H 3 (CH 3 )OCgH 7 V m 267*5 


CH 


CH,/ 


CH—CH 

*\,CH—C^ ^C—CH, 


Cio^is 181*0 
™ 10*0 


\ 


=CH 


/ 


& 

c 3 h, 


70*0 


o-c 9 h 7 


2nVa 26l*0 
Vm 267*5 

A = + 6*5 2 X 3*2 (C 7 —C B ) 


Heptyl thymol C 8 H 7 . C 6 H 3 (CH 3 )OC 7 H 15 V w = 369*5 

^10^13 iSi'O 


CH—CH 

CH *\ / \ 

\CH—C x C—CHg 

ch,/ \ / 

C—CH 

I 

o-c 7 H ]5 


O' 10*0 
C,H J5 i 59 'o 

2 »V* 350-0 
Vm 369-5 

A = + 19-5 6 X 3-2 (C u - C 6 ) 


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ORGANIC COMPOUNDS CONTAINING OXYGEN. 131 


Octyl thymol C,H, . C,H,(CH,)OC 8 H 17 V* = 396-5 

CH—CH C «* H i? 181-0 

CH v O io*o 

>CH —or ^C—CH, C 8 H 17 182-8 

CH,/ \ / - 

C=CH 2 »Va 374*8 

I V« 396*5 


6—c 8 h 17 


A = + 21*7 7 x 3*i (C 13 -C B ) 


The increase in volume for complexity is seen to be appar¬ 
ently linear. This increase starts from approximately the same 
point in all the series, viz. where the total complexity of the side 
chains is C 4 . Apparently it does not matter whether the chains 
are entire , or divided up , for this to occur . This indicates an 
increase in volume due to a corresponding increase in com¬ 
plexity as distinct from an increase in length of chain. The 
increase starts from C 5 which is similar to what is observed in 
open chains. We conclude that the nucleus exerts no influence 
at all. Octyl thymol is interesting, as being the most complex 
compound which has been studied in this work. It consequently 
possesses the largest volume which is one of nearly 400 units. 

The calculation of the volume of an ether of the type men¬ 
tioned is as follows :— 

p Cresyl heptyl oxide. 


CH,—C,H 4 — 

-OC 7 H 15 

C.H. 

8g*6 

CH, 

25*5 

O' 

11*0 

c 7 h 16 

158-9 


285-0 

c,—c 4 

+ 12-8 (4x3-2) 

SnVa 

297-8 

Vm 

298-3 


The o y my and p Cresylic Ethers . 

It has been shown that when two groups occupy the 
ortho-position, there are usually contractions. 

C 8 H 4 =8g*6 CH 8 =25'5 C 2 H 5 =48 0 '= 7*4 or iro C»—C 4 =3*2 (#—4). 
o m p 


^ CH 

CH 

cu 





CH 


/ 


— ch 3 — 1 CH 3 

CH CH CH OH 

CH C—O—R CH CII 

^CH^ ^qZ-O—R 

9 * 


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132 


LIQUID CHEMICAL COMPOUNDS. 


Groups CH 3 and OCH s 
146-4 

I47’8 

148*0 

2nVa 

148*0 

A -1*6 

-0-2 

± 0 


CH„ OC a H 5 

171-2 

1727 

172*8 

173*1 

-1-6 

-0*1 

+ 0 


CH,. OC 8 H 7 

195*4 

1967 

196-5 

195*1 

- i-i 

• — 

± 0 


ch 8 , oc 4 h 9 

218-8 

221*0 

221*3 

221*4 

-25 

-0-3 

± O 


CH 8 , OC 7 H 1b 

2936 

297*4 

298-3 

298*0 

-47 

-0*9 

+ O 


CH„ OC 8 H„ 

3I8-6 

3227 

323*1 

323*4 

-4*5 

-0*4 

± O 



The magnitude of the contraction evidently increases as 
—OR becomes more complex, thus showing the existence of a 
special relation between the two groups. 

There is thus a large contraction when the groups are in the 
ortho-position relative to each other. This appears to increase in 
magnitude as the complexity of R increases. The above con¬ 
tractions are regarded as being due to a mutual action of the 
group, owing to residual affinity. 

The following compound is worthy of separate study:— 


Dimethyl resorcin. 


157*7 

C-och 8 

c 6 h 4 

89*6 

\ 



CH CH 

20' 

14*8 

1 H 

C C—OCH 8 

2CH 8 

52*o 

\ / 



CH 

2nV a 

156-4 


v m 

157-7 


The oxygen atoms are probably augmented in value, as com¬ 
pared with its value in previous compounds, owing to the fact 
that there are two—8*0 e.g. The value of O' in - OCH s is, 
however, still considerably below that for O . C 2 H 6 - io units. 
It will have been repeatedly observed that the methyl group 
always causes a diminution in volume as compared with the 
ethyl, etc. 


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ORGANIC COMPOUNDS CONTAINING OXYGEN. 133 


Oxygen with Double Linking. 

= o. 

(Attached to carbon.) 

The simplest compound is— 

Carbon monoxide < C = O V wt 22*1. 

Carbon in this instance is divalent, and it has not been shown 
whether divalent carbon possesses the same volume as quadri¬ 
valent carbon or not An examination of such groups as CHO 
and CO, under certain circumstances , shows that in combination, 
CO = 22*1. 

C 8 H 7 . CHO 96 0 
^ 3^8 74 *° 

CO 22*0 


It follows that the oxygen under these circumstances (i.e. 
when carbon is quadrivalent C iv ) is the same as when it is 
divalent. 

O" = (CO - C) = 221 - 14-8 = 7 3 (H a ) 

Carbon dioxide C [( V« «*n 


V« 33*0 


The volume of C = 14*8 .*. O a = 187. 

It is remarkable that the volume occupied by 0 2 is the same 


as the volume of 0 2 in the esters - Cn 


and similar to the 


as cue vuiumc ui w 2 in uic cslcis — V '\0(R) a,Ilu Slllllliu LU U1C 

one calculated from the acids - C^5 /t rv. 

Moreover if the volumes of certain compounds containing the 
group - C^q are considered, these compounds being derivatives 
of the acids, we see that the volume of : O is 11 *o. 

CHo- Cr r»" _ ^ _l oo. T \ _ 


O" = 74-(25-9 + 14*8 + 22*1) = 11*2. 


Moreover [O"] = 33*5 - 22-1 == 11*4. 

It is possible that the two oxygen atoms may possess 
different volumes (a) [O'] = 7*4(2!!), (b) [O''] = ii o(3H). 

[O"] . 11*4 ) 

- Cf [ i8*8 for 0 2 

\0H [O'] = 7*4 J 


- Cf [O"] = (48-0 - 14-8 - 22*1) = iro. 
\C 1 


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134 


LIQUID CHEMICAL COMPOUNDS. 


An alternative supposition is that the volumes of oxygen 
(O'') are similar, i.e. [O"] = i8‘8 -s- 2 = 9*4. 


The Aldehydes and Ketones. 

In dealing with compounds which contain doubly bound 
oxygen, we come to the conclusion that the position of this atom 
in the side chain has some influence on the volume. Comparing 
the ketones and the aldehydes we find:— 

CH 8 . CH 2 . CH CH g —C—CH 3 

II II 

o o 


Acetaldehyde Vm = 74*8 
CH 3 . CH 2 . CH 2 . CH 
. II 
O 


Acetone Vm = 77*1 
CH 3 . CH a . C . CH 3 
II 

O 


Methyl ethyl ketone V« = 96*7 
CH 3 . CH a . CH 2 . C . CH S 
II 

O 

Methyl propyl ketone Vm = 118*5 
CH 3 . CH 2 . C . CH a . CH 3 
II 

O 

Diethyl ketone Vm = 117*7. 

These compounds are difficult to deal with. 

(a) On the one hand, we have one factor involved, which is 
the position the compound occupies in its particular series. 

We should expect the acetaldehyde and acetone to be rela¬ 
tively larger than the volumes calculated on the basis of C=* 14*8, 
H = 37, and thus be not quite comparable with the succeeding 
members of each series. 

(b) There is also the question of the influence of symmetry- 
Both of these factors might be considered to be of influence on 
the volumes, and to explain the differences. 

Observation, however, shows that there is something wanting 
in this kind of explanation. 

The study of molecular volumes has made the want of a com¬ 
prehensive generalization, which would cover all these cases, very 
keenly felt. The good results which have attended the study of 
some series show that we are getting nearer to the discovery of 
such a generalization. 

If we relinquish such purely geometrical ideas as symmetry, 
and introduce the more chemical notion of a specific influence of 


Propaldehyde Vm = 96*0 
CH 3 .CH 2 .CH 2 .CH 2 CH 
II 

O 

Butyraldehyde Vm = 118*2 


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ORGANIC COMPOUNDS CONTAINING OXYGEN 135 


certain atoms or groups, we seem to be getting nearer to the 
desired end. After all, the question of symmetry may be in¬ 
volved, but only in a subordinate sense. The particular arrange¬ 
ments of the atoms in a compound are bound to have some 
influence on the volume, and among them their symmetrical 
arrangement about the distinctive atom or group of the compound. 
It is possible for there to be a yet more fundamental explanation, 
which may lie in the direction of the alternative one already 
suggested. 

It must especially be noted that the volume variations in the 
series of compounds including the aldehydes and ketones of 
various kinds seem inseparably connected with similar variations 
in the boiling-points. Compounds with: O at the end of the chain 
have the smallest volumes and boiling-points. The volumes ap¬ 
parently increase as : O becomes attached to intermediate carbon 
atoms. 

It has been shown that when the iso group is present in a 
pure hydrocarbon (paraffin, etc.), there is a contraction. 

ch 3 —ch—ch 2 —ch 3 

r a = — o-s 

I'M, 

CH, 

CH 3 —C—CH a —CHg A = - 2 x 0*5 = - ro 

These contractions are connected with the presence of methyl 
groups which probably are not saturated. In such a modification 
as— 

CH 3 —C=CH—CH S 

L a = " 2 ’ 4 

there is an increase in the contraction, owing to the presence of 
the. ethenoid linkage, in close proximity to the iso group. In 
some paraffin derivatives we, however, get a different result:— 


CH,—CH—Cl 

in, 

CH a — CH—CH„—Cl 

U 


A = +2*6 

A = + 1*5 


Whilst the association of two hydrocarbon radicles, or a 
hydrocarbon radicle and one which contains an ethenoid linkage, 


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136 


LIQUID CHEMICAL COMPOUNDS . 


occasions a contraction, the association of a hydrocarbon group 
and a halogen atom produces an expansion. It is evident that 
the methyl CH 3 group exerts a more powerful influence than 
an ethyl group, and the extent of the influence of the halogen 
atoms is in the order indicated by chlorine, bromine, and iodine. 

In studying the groups, we find that there is a depressing 
effect due to the simple radicle, which diminishes as this becomes 
larger. The effect is thus in the inverse order of— 

H, CHg—, C a H s —,*C a H 7 —. 

We have now to consider the influence of H, CH 8 , C 2 H 6 , etc., 
on C : O. As in the halogen compounds, the substitution of: O 
for H 2 increases the volume. The atom hydrogen does not seem 
to have much effect, but that of the methyl group is considerable, 
whilst it is progressively smaller for C 2 H 6 and C 8 H 7 — 


/H 

(1) ch, . cr 
'' \o 

Vm= 567 

2nV a 

51*9 

A + 4*8 

(CH S and H) 

/h 

(2,C ’ H ‘<o 

t 

II 

60 

>» 

74 *° 

+ o*8 

(C s H 5 and H) 

/CH, 
( 3 ) CH, . / 

\o 

V w = 77*1 

•• 

74 *o 

+ 3*1 

(two CHg) 

/H 

4 ) c,h 7 . / 

\o 

II 

% 

6 

»» 

96*0 

— 

(C 3 H 7 and H) 

/CH, 

( 5 ) C,H,.C( 

\o 

V m = 967 

>» 

96*0 

A + 07 

(CH 8 and C 2 H 5 ) 

/H 

(6) c 4 h,.c; 

\o 

V m = n8*2 


Il 8’2 

A — 

(C 4 H 9 and H) 

/CH, 

(7) c,h 7 .c( 

\o 

/C,H, 

(8) C,H,. c; 

\o 

V w = 118*5 

»> 

118*2 

A + 0*5 

(C 8 H 7 and CHg) 

V w = 1177 

>» 

Il 8*2 

> 

1 

0 

ut 

(two C 2 H b ) 

It is seen that wherever we find one 

or two 

methyl groups 


we find a large positive effect. That due to the C 2 H 6 group is 
less. 

Whilst the above seems clear, we must also consider another 
factor—the total complexity of the compound. The effect of the 
methyl group diminishes as the total complexity increases. In 
number (8) the combined effect of complexity and the C 2 H 5 
group is to produce a negative difference, but in number (7) the 


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ORGANIC COMPOUNDS CONTAINING OXYGEN. 137 


expanding influence of the CH 3 group is sufficiently great to 
convert this into a positive difference. It is extremely probable 
that were complexity alone operative, the relative volumes would 
steadily diminish to a minimum at the first member of the series. 
Seeing, however, that the first members in each series include 
the methyl and ethyl groups, there is a contrary or expanding 
influence which is a maximum at the first member of each series, 
and this more than balances the effect of diminishing complexity. 

The Aldehydes. 

It is evident, as Kopp himself discovered, that the aldehydes 
possess similar volumes to those of the paraffins, so that : O may 
be supposed to occupy as much space as two volumes of 
hydrogen. 


TABLE LIX. 


The Aldehydes. 

Acetaldehyde CH S . CHO 

Propaldehyde CH S . CH S . CHO 

Butyraldehyde C 8 H 7 .CHO 
Valersddehyde C 4 H 9 . CHO 
Benzaldehyde C 6 H B .CHO 


v m . 

v M . 

The Paraffins. 

567 

— 

C a H, 

74-8 

—. 

c»h 8 

96*0 

96*0 

c 4 h 10 

Il8*2 

117*8 

C»H ia 

118*4 

118*2 

C.Hj. CH S 


[s 0] = 7 ’ 4 . 


The two series are strikingly similar, so that we may suppose 
that the volumes of the simpler paraffins resemble those of the 
aldehydes. 


Acetyl chloride CH S . COC 1 
H 


H—C—C . 


A i 


Vm 74*1 
CH S 26 0 
C 148 
Cl 22*2 
O" iro 

SnVd = 74*0 
Wm = 74*1 


Chloral C^HO. Vm 106*37. 


Cl—c—c = 0 

V CCI3H 

84*5 

n 

less H 

-37 



80 *8 


CHO 

25*9 


2nV a 

106*7 


Vm 

106*37 


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LIQUID CHEMICAL COMPOUNDS ,, 


138 


Trichloracetyl chloride C 8 C 1 4 0 . V», = 125*5. 


Cl 

1 


V CC1 3 

c 

0" 

8o*8 

14*8 

ii*i as in - C0"C1 

Cl-C — 

1 

- 0 

II 

0 

Cl 

22*2 

1 

1 

2 »v a 

128*9 

. Cl 

Cl 

less for ai 8 subst. 

-3* 1 



2»Va 125*8 
V w 125*5 


The Ketones. 

Acetone CH 3 —CO—CH S Vw 77 * 1 * 

The volume is considerably larger than that of the isomeric 
propaldehyde, from which we might conclude that the volume is 

[:0] = 74 + 23 = 97- 

The following methyl ketones, except the third and fourth 
which are interpolated, have been investigated by Thorpe. 


TABLE LX. 


The Methyl Ketones . 44 


Compound. 

C 2 H 5 . CO . CH S 
C 3 H 7 . CO . CH S 
C 4 H 9 . CO . CH 3 
c 5 h u . CO . CH 3 
c 6 h 13 . CO . CH 3 


v„. 

v w . 

The Paraffins. 

967 

96*0 

c 4 h» 

118-3 

117*8 

C 5 H i2 

;i 4 o-i) 

139*9 

C.H 14 

162-8) 

162*6 

C,H 1# 

186-6 (Sch.) 

186*3 

c 8 h I8 


The volumes of these methyl ketones are a little larger than 
those of the corresponding paraffins. 


Pinacolin 

ch 8 ) 

CH. J-C . CO . CH„ 

ch 3 


c.h 12 o. 


less for 


Vf» 138*5. 

^6^12 I 3 2 *4 

O 7*4 

139*8 

^group - i*2 
- 138*6 


SnVa for pinacolin C tf H 12 0 2 (139*8) is not far from that of 
C 6 H 14 nor from that for C 4 H 9 . CO . CH 3 the normal compound. 

The value of the group is about equal to two iso groups. 

Since CH 3 . COC 1 represents the acetyl group + a chlorine 
atom we see that : O may possess a volume larger than 7*4, one 
in fact equal or nearly equal to iro. 


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ORGANIC COMPOUNDS CONTAINING OXYGEN. 139 


An interesting case is that of 


Acetoacetic ester C 6 H 10 O 3 . 

V m 153*6 

CH 3 —C—CH 2 — 

11 \oc a H 5 

0 


The compound has 

V w 150*5 

CH 3 —C—CHj-C^ 0 

II \OCjHj 

A + 3*1 


If the constitution of acetoacetic ester were “ enolic ” 


CH3-c • CH 

OH 


C 


^ OC2H5 


the volume would be similar to that of ethyl butyrate, or even 
less as the matter stands, the constitution cannot be other than 
“ ketonic *\ 

This is interesting from a chemical stand-point, and confirms 
the conclusions derived from other sources, both chemical and 
physico-chemical. 

There is one point which may have an important bearing 
upon unexplained variations in atomic volumes from the normal 
when we form a more or less complex substance by the union or 
condensation of two simpler ones, one particular atom of which 
has a definite value in one compound, and remains unaltered in 
the complex one. Thus in the synthesis of aceto-acetic ester:— 


ch -< 


H 


CH S . COO Et 


CH S . C-CH a • COO Et 

II 

o 

The atom O" is thus similar to carboxylic oxygen in ethyl 
acetate, and is also similar to the atom in:— 

CH -<C, 


The group—CH S CO is really an acetyl group and O" only 
apparently resembles a ketonic oxygen. 


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140 


LIQUID CHEMICAL COMPOUNDS. 


One other compound remains, also interesting, from a chemi¬ 
cal point of view, viz. Camphor 

Camphor C 10 H 16 O. V m 1877. 

CH S -CH-ch 2 We can obtain its value from that of 

borneol Vm 190*5. 

Group OH = 6*o •+■ 3.7 = 97 

c io H i5 = I 9°*5 - 9*7 = 180*8 
less H 37 



57 x 37 
less for ring 

2 tNa 

Obs. 


0" 

2 nV a 

218*3 
- 30*0 


177*1 

11*0 

188*1 


188*3 

187*7 


The Carboxylic Acids . 45 

The aldehydes and ketones give rise to the 

and 


(a) R “ C \ oh and W R — 1 Cf 


\0R 

Carboxylic acids. Carboxylic esters. 

These compounds contain the oxygen atom * O • 
doubly-bound one : O. 


and the 


TABLE LXI. 


Substances. 

Vm. 

»CH S . 

A for O x . 

Propionic 

. . . C,H,O a 

85-3 

66-3 

19*0 

Butyric. 

. . . C 4 H 8 O s 

107*8 

00 

00 

19*4 

Valerianic 

. . . C fi H 10 O 8 

130*0 

iio*5 

19*5 

Caproic. 

• • • CjHijOj 

152*5 

132*6 

19*9 

Heptoic 

. . . C 7 H 14 O a 

174*6 

iss^ 

19*4 



Mean value = 

19*5 


These acids are altogether exceptional, in that, although they 
contain the hydroxyl group, their volumes are by no means 
diminished in consequence. 


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ORGANIC COMPOUNDS CONTAINING OXYGEN 141 


The value of: O may be obtained as follows :— 

TABLE LXII. 


The Fatty Acids. 

V m . 

0 ". 

v w . 

The Paraffins. 

C.H.O, . . 

853 

n *3 

74*0 

C,H S 

c 4 h 8 o, . . 

107*8 

n*8 

96*0 

c 4 h 18 

C,H 10 O, . . 

130*0 

12*2 

117*8 

C.H„ 

C 6 HiA 

152*5 

12*6 

139*9 

c«h 14 

C 7 Hi 4 0 2 

174-6 

12*0 

162*6 

c 7 h„ 


The average value of O” is 12*0, the assumption being that 

[*0*] = 2 H 

for [ 0 "] + [O'] = 12 x 7*4 = 19-4- 

The value of O" can also be obtained from the compounds 
containing the group - C\Q* 


Phosgene Cl - C! 


\ m 7 °'° 


/° 

\ci 

O" = 74*0 - (148 + 2 x 22*1) =* 11*0 


Acetyl chloride CH, - C: 


-c/° 


\ci 


M.V. 74*0 


Q^' = 74*0 - (14*8 + 25*9 + 22*1) = ii *3 


From acetic anhydride we obtain the value of O' 


CH 8 . CO . O . CO . CH 8 
2 Vols. CHj,. COOH 
CH S . CO - O . CO . CH 8 


M.V. 109*9 
125*6 
109*9 


H a 0 157 

H 2 7*4 

•O* 8*3 

O" + O' = n*3 + 8*3 = 19 * 6 . 

The excess is thus thrown on to the O" or on to the O' 
according to the method of calculation. 

The simplest explanation is to suppose that [ 0 /7 ] = 3[H] 
and [O'] = 2[H]. 

Then, assuming that 0 2 = 19 5 

[O"] =* 11*7 and [O'] = 7*8. 


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142 


LIQUID CHEMICAL COMPOUNDS. 


The Methyl Esters . 46 

The methyl esters are sharply distinguished as regards the 
volumes of oxygen from the acids on the one hand, and from the 
more symmetrical esters on the other. 


TABLE LXIII. 


Radicles. 

The Acids . 

The Methyl 
Esters . 

Symmetrical . 

Vm. 

A. 

v w . 

A. 

v w . 


CH S —CO— 

853 

- 2*1 

83*2 

+ 1*4 

84*6 

H . C0 2 C 2 H 5 

C 2 H 5 —CO— 

107*8 

-3*2 

104*6 

+ i*5 

106*1 

CHg . C0 2 . C 2 H 6 

CgH ? — CO— 

130*0 

-3*3 

1267 

+ 17 

128*4 

CH, . C0 2 . C 3 H, 

C 4 H 9 —CO— 

I 5 2 '5 

“3*4 

149*1 

+ i*4 

150*5 

C 3 H, , COj * CjHg 

C 5 H u —CO— 

174-6 

“2*4 

172*2 

+ 1*8 

174*0 

C s H 7 . CO a . C,H, 

Mean = 

-2*9 

Mean = 

+ 1-6 




We find that by comparing— 



and also 


- C \OR 


and —Cf 

\OCH, 

A -2*9 


and 

A +i*6. 


_C^° 

\oCH, 


This result is quite different from that shown by the alcohols 
CH 2 . OH, as compared with CH 2 O . CH 8 and CH 2 —O—R. 

The alcohols are depressed, whilst the acids are augmented in 
volume. 

As regards the ethers and esters, the O—CH 8 group produces 
a diminution in volume in both. 


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ORGANIC COMPOUNDS CONTAINING OXYGEN. 143 


TABLE LXIV. 
Monocarboxylic Esters. 
(Second Series.) 


Substances. 

v w . 

»CH 2 (22*l). 

o 2 . 

HC 0 . 2 CH 3 .... 

62*6 

44*2 

18*4 

HC 0 2 C 2 H 5 .... 

84-8 

66*3 

* 8-5 

H . COjCjH, .... 

106*4 

88*4 

18*0 

CH,. CO a C,H 7 . . . 

128*8 

110*5 

i 8*3 

c 2 h 5 . co 2 c 8 h 7 

151*0 

132*6 

18*4 



Mean value = 

18*3 


TABLE LXV. 


The Esters. 
C#Hjj«O a . 

v w . 

0". 

v m . 

The Paraffins. 
C»Han + 2* 

HCO a CH 3 . 

62*6 

11*0 

51*6 

CjH 8 

hco 2 . C a H 6 . 

84*8 

10*8 

74-0 

C s H 8 

h.co 2 .c 3 h 7 . 

106*4 

10*4 

96*0 

C.H W 

CHg . CO a . C 3 H 7 

128*8 

11*0 

117*8 

C 5 H ia 

c 2 h 5 . C 0 2 . C 3 H 7 

151*0 

ii*i 

139*9 

C.H„ 


Mean = 10*9 




Thus assuming that [. O'.] = 7*4 (2H) [O"] = 10*9 
[O"] + [O'] - 7*4 + io *9 - i 8 * 3 . 

We thus have— 


for the acids 

O, 

19*5 

O" 

117 

O' 

7-8 

the methyl esters 

o a 

16*6 

0" 

11*0 

0' 

56 

and the symmetrical esters . 

o a 

18*3 

0" 

11*0 

0' 

7‘4 


There is distinct evidence that [O"] = 3H and [O'] = 2H 
throughout the series, in the following:— 


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144 


LIQUID CHEMICAL COMPOUNDS. 

TABLE LXVI. 

Symmetrical. 






Esters. 

V m . 

Vm. 

Ethers. 

CnHjnO. 

C a H 4 O a 

62*6 

62*5 

Cn H a n-f- a O 

c 8 h 6 o 

C.H.O, 

c 4 h 8 o. 

84*8 

106*4 

106*4 

c,h 8 o 

c 4 h 10 o 

C 6 H 10 O a 

128*8 

128*0 

C,H w O 

C 6 HiA 

151*0 

i5i*3 

c,h 14 o 

c,h 14 o. 

i 74-6 

174*7 

C 7 H t i,0 

^8^16^2 

*97*7 

197*7 

c 8 h 18 0 

<^° d 

^10* 1 30 U 2 

221*9 

221*1 

c»h m o 

245*9 

246*1 

C 10 H ffl O 

CnH M O a 

270*3 

271*3 

C n H M 0 

^12^94^2 

295*9 

295*5 

C u H„0 

^14^28^2 

35i*2 

353*4 

C 14 H m O 

^15^80^2 

377*0 

377‘6 

Cj.H.,0 


4°4*3 

404-5 

c 16 h m o 


Thus, in spite of the change due to complexity 
[O'] - 2[H] and [ 0 "] = o 0 ] = 3 [H] 

under ordinary conditions [O'] = 7*4 [O"] = [> O] = 11*0. In 
both series we find contractions when the group - OCH 3 is 
present (a) A diminution of about — i -o in the ethers and ( b ) 
a diminution of - i*8 in the esters. This may be due to a 
contraction of the O' atom alone, of the whole group, or of only 
the CH 3 group under the influence of the oxygen atom. 


The Effect of the Homologous Increment CH 2 on the 
Volumes of the Monocarboxylic Esters. 

These compounds have been studied chiefly by Gartenmeister 
(loc. cit.), Schiff, and Elsasser. 

The series of the methyl esters may be made use of to illus¬ 
trate Lossen’s method of calculating the volumes of series of 
compounds. 

Thus, the volume of methyl formate HCOOCH 8 is V m 627, 
and the difference between this volume and that of methyl 
acetate CH 3 . COOCH 3 is A = 20*5. 

The assumption is made that the volume of the homologous 
increment CH 2 increases by 0*5 from term to term. 

Thus for any compound C»H 2 » 0 2 

Vm = 627 + (» - 2) 20*5 + 0*5 ~ 2 ) 8 (1) 

2 


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ORGANIC COMPOUNDS CONTAINING OXYGEN 145 
Now Kopp had made the assumption that 

[HJ = [O], (for both O' and O") 

and this, combined with the assumption that the average initial 
difference for CH 2 , is 

A CH a = 20*9 

enabled Lossen to calculate from methyl formate 
C 2 H 4 0 2 . V m =b 627 

the values [C] = 10*45 [H] = 5*225 [O] = 10*45 

Then the above equation becomes 

V#» = I0*45» + 5*225W + 10*450 + o*25(» - 2) 2 , 
and by its aid, the volumes of the different members of the series 
can be calculated. 

A different method is adopted here, which is based on the 
idea that whatever may be the changes in volume in a homol¬ 
ogous series, the relative volumes remain the same throughout. 

If we assume that 

c = 4 h, O' = 2H, O" = 3 H 

in the formic esters, we may obtain a curve which shows how the 
atomic volumes change throughout the homologous series. This 
is accomplished by finding the sum of the hydrogen equivalents 
in the different compounds, and the quotient of the volume 
V m and this sum W, gives the volume of hydrogen in a particular 
compound. By this means we avoid the necessity of making 
use of the difference in volume between two consecutive members 
of a series, which is neither true for the one compound nor the 
other. 

Thus for compound C»H 2W 0 2 

Vm = (6» + 5)S = WS. 


TABLE LXVII.— Volumes of the Atoms in the Formic Ester Series. 

CmH 2 » 0 2 . 


Compound. 

w. 

Vm. 

Vm 

W* 

Methyl formate 

. hco 2 ch 8 

17 

627 

3*688 

Ethyl „ 

. HCO s C 2 H fi 

23 

84*6 

3*678 

Propyl „ 

. HC 0 2 CoH 7 

29 

106*2 

3*666 

Butyl „ 

. HCO 2 C 4 H 0 

35 

127*6 

3*645 

Amyl 


4 i 

150-5 

3*671 

Hexyl „ 

. hco 2 c 6 h 18 

47 

173*3 

3*688 

Heptyl „ 


53 

196*7 

3 * 7 H 

Octyl „ 

. HCO a C 8 H 17 

50 

220*3 

3*734 


IO 


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146 


LIQUID CHEMICAL COMPOUNDS / 



10 20 30 40 50 60 

Number of H Equivalent's. 

Fig. 6. 


The above curve shows how the volumes of the atoms, and 
thus of the group CH 2 , vary in the formic ester series. 

The curve is very similar to the methyl ether curve, and 
shows a well-marked region of diminishing values of V/W. The 
region of the minimum is here reduced to a point, as the curve 
is formed by the intersection of two others. The ascending 
curve is as far as we can make out linear, with a value of 
A V/W = 0*022 on the average. The curve as a whole, whilst 
in many respects resembling that for the normal paraffins, is in 
others quite different 

These curves do not seem capable of exact mathematical 
formulation, but this is not of great consequence, as the mole¬ 
cular volumes of compounds are calculated in quite a different 
way. It is much better to consider the total variation from a 
volume calculated from mean values, and regard this total 
variation as due to general or particular constitutive influences. 
An estimation of the values of these is often possible. The 
curves are, however, useful in showing how the atomic volumes 
vary in a series, and also in indicating points of similarity or 
contrast with the curves for other series. 


Digitized by v^ooQle 






ORGANIC COMPOUNDS CONTAINING OXYGEN. 147 

So far as the methyl ester series is concerned, we find that— 

S' = 3*645 + (6 n ~+~5 - 35) x 0*0037 
since 1/6 of 0*0022 is = 0*0037 

and the total volume of a compound is 

Vtn = ( 6 n + 5) {3*645 + (6 » - 30) x 0*0037}. 

If we compare the volumes of certain of these compounds, 
we get the following constants:— 

H.COOCH3 v m 6270 

H . COOC 6 H 18 Vtn 173*30 

5CH a 110*6 CH a 22*12 

Since H . COOCH 8 is C a H 4 O a 

O a = 6270 - 44*24 = 18*46 

NOW O" II ^} 18-5 for ° a CH » = 22-1 - 

Although the results obtained by Lossen's method and the 
one just described are both in good accord with the experimental 
results, yet there are some points of difference between them. 

The most important of these is the difference in the curves 
representing the atomic volumes in different members of the 
series. 

Lossen assumes that the expansion is rectilinear from the 
first compound, whereas the curve just indicated shows a con¬ 
traction to a minimum at the fourth member and then an ex¬ 
pansion. In this respect the methyl ester curve is similar to all 
the other curves studied. 

The Methyl, Ethyl, and Propyl Salts of the Fatty Acids. 

This is an arrangement of the esters which is quite different 
from the other. In the first, the acid is the same, but the alkyl 
groups are different; in this arrangement the fatty acid radicles 
are different, but the alkyl group is the same for all. It by no 
means follows that the relations between the atomic volumes are 
the same in the two methods of arrangement. It has been 
found that better results and smoother curves are obtained by 
utilizing Schiff’s data as well as those of Gartenmeister. The 
methyl ester curve is wholly from Gartenmeister’s results, the 
ethyl ester curve is partly due to Schiff* and partly to Garten¬ 
meister, whilst all the values employed in the formation of the 

10 * 


Digitized by v^ooQle 



148 LIQUID CHEMICAL COMPOUNDS, 


propyl curve are due to Gartenmeister except that for propyl 
propionate. 

We give below a diagram showing the volumes of the esters 
of formic and acetic acids. There is a very great difference 
between the first part of the two curves. On comparing the 
formulae 

H - COOR CH S - COOR 

The formates. The acetates. 


we see that this difference is to some extent connected with the 
different effects of the two groups 


H 



and 



The CH 3 group again is responsible for a contraction. It is, how¬ 
ever, difficult to analyse the data completely, because at this point 
the effect and change due to complexity is enormous. The best 
results are obtained if we can compare the volumes of different 
compounds of similar complexity. Some of these effects are very 
complex, and are the sum total of the combined effects of the 
atoms and groups. 



Number of H Equivalents 

Fig. 7 . 


Digitized by v^ooQle 




ORGANIC COMPOUNDS CONTAINING OXYGEN. 149 


H 

< 

fa 

W 

X 

H 


J 

<< 

CO 

>« 

a, 

O 

% 

a. 

Q 

2 

< 

S 

>* 

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H 


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13 

CO 

I 


2 

13 

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3 

w 


fit 

vo 

8 

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00 

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pt 

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vp 

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In the above table, we notice the general effect of change 
of complexity on the atomic volumes, and this is also indicated 
by the curves. These curves are totally unlike those shown to 
be applicable to the esters of the same acid. They, however, 
resemble the curves for the normal paraffins and other com¬ 
pounds. (a) The descending portion is more pronounced for 


Digitized by v^ooQle 




150 LIQUID CHEMICAL COMPOUNDS . 

the methyl salts than for the others, for the reason that the 
simplest compounds of the series have shorter chains, and are in 
general of smaller complexity. ( [iY) The curves are wide and 
open, especially that for the methyl salts. This is totally unlike 
the curve for the methyl ethers or for the esters of formic acid 
which are broken at the minimum, owing to an abrupt change in 
the curvature. 



10 20 30 40 50 60 70 

Number of H Equivalents. 

Fig. 8 . 


An Examination of the Causes of the Variation of the 
Volumes of Isomers, and a Consideration of the General 
Question of the Influence of Symmetry. 


It was shown by Gartenmeister that the volumes of com¬ 
pounds possessing similar formulae, but differing in the method 
of the distribution of the carbon atoms between the O and C 
radicals, possess somewhat different volumes. Thus in a com¬ 
pound 


R—C 


\ 


o 

OR' 


R and R' may have different complexities, and the volumes of 
the compounds depend on this circumstance to some extent. 
Similarly the boiling-points vary. 

The following series shows this. 


Digitized by v^ooQle 





ORGANIC COMPOUNDS CONTAINING OXYGEN 151 


TABLE LXIX.— The Isomeric Esters of Formula C 8 H 16 O a . 


Compound. 

Vm. 

b.p. 

C 6 H 13 . COOCH3 

C 5 H 12 . COOC 2 H 5 

196*2 

173*0 

1977 

167*0 

C«H n . COOCjH, 
C 8 H 7 . COOC 4 H 9 
ch 8 . COOC 6 H 13 

197-8 

167*0 

197-8 

165-7 

197-7 

169*0 

H . COOC 7 H 15 

196-7 

176*0 


The volumes are seen to be a minimum at the extremities 
of the series, and a maximum at the centre. The opposite is 
true of the boiling-points. 

This has been ascribed to differences in the symmetry of the 
molecules. Compounds in which the radicles differ most, possess 
the smallest volumes, and those in which they are most nearly 
equal possess the largest volumes. The latter are the most sym¬ 
metrical compounds, and the former the least symmetrical. We 
believe that a consideration of such influences as symmetry, 
which are incapable of accurate measurement, is undesirable and 
that it will be better to substitute considerations of the specific 
influences of groups. 

Influence of the C and 0 Groups . 

In the above compounds the groups 

- O . CH 8 and H . C =5 

produce contractions of - I *6 and - I * 1 respectively. The former 
group is a frequent cause of contraction in volume as will be seen 
from Table LXVIII on the methyl and ethyl esters. The mean 
difference between the volumes of methyl esters and those of the 
corresponding ethyl and propyl compounds is - 1 -6, a number 
which is exactly similar to the one just given. The volumes of 
the methyl esters are thus below the normal, whilst it may be 
shown that the symmetrical compounds are normal. 

Thus for 

HCO a C a H 5 Vw 84*6 
C 2 H 5 48*0 
CO a 33 3 
H 37 


SttVa 85*0 
Vm 84*5 

The volume of 

ch 8 . co 2 . CH S Vm = 83*2 
is thus 1 *4 below the normal, 


Digitized by v^ooQle 



152 LIQUID CHEMICAL COMPOUNDS. 

This is no doubt due to the methyl group, since a similar 
feature is noticed in the case of other methyl compounds. 

It is, however, necessary to also take into consideration 
other groups in a compound, and possible interactions. 

Thus in the salts of formic acid we note the following 


H . CO a CH, 

. V m 627 

17 x 3*7 = 62*9 

A 

- 0*2 

H . CO a C 2 H 5 

84*6 

23 x 3 7 = 85*1 

A 

- 0-5 

H . CO a C,H 7 

106-2 

29 x 3*7 = 107-3 

A 

- i-i 

H . C 0 2 C 4 H 9 

127*6 

35 x 3*7 = 129*5 

A 

- i *9 

H . CO a C 5 H n 

150*5 

41 x 3-7 = 1517 

A 

- 1*2 

H . CO a C # H n 

173*3 

47 x 3*7 = 173*9 

A 

- 0*6 


Thus the contraction increases as the group increases, up to a 
certain point, and then diminishes. (See also curve.) 

These effects are no doubt complex, and the exact analysis 
of the data is difficult. Much depends on the exact configuration 
of the molecules, and the particular groups acting. The first is 
a subject about which comparatively little is known. Another 
of the complications is, as already shown, the influence of sym¬ 
metry. 

It will be noted that the series 

(a) R—COOH aliphatic acids A 

(b) R—COOCH, methyl esters 

(c) R—COOCjH 5 ethyl esters 

R—COOR' higher esters. 

are truly homologous series, if we are to judge by the constancy 
of the differences A between the corresponding members of pairs 
of series. 

On the other hand, if we arrange the substances as different 
salts of the same acid, complications are introduced, if we are to 
judge by the variable character of the differences A. For this 
reason, these series are not regarded as truly homologous. By 
the first method of arrangement, we notice that the group CH 8 , 
attached to the atom O, is responsible for a constant difference 
A = — i*6, and is thus independent of the complexities of the 
compounds. Similarly, the group C 2 H 6 is found to be responsible 
for a smaller diminution. By comparing the volumes of isomeric 
compounds we notice this depressing influence of CH a , QHg, 
etc., both when attached to the O radical and the C radical, and 
moreover the amount of the contraction can be estimated. This 
method gets rid of the complicating influence of complexity. 


Digitized by v^ooQle 




ORGANIC COMPOUNDS CONTAINING OXYGEN 153 


Any depressing influence of particular groups is also revealed by 
an examination of the curves. 

We obtain similar results from an examination of the di- 
carboxylic esters, 47 but the depressions are comparatively small. 


Compounds: 
Methyl oxalate 

V. 

»ch 2 . 

Or 

(COOCH,), 

COOCHg 

“ 7*4 

81 *o 

2 X 18*2 

dooc a H, 

139*6 

103*2 

2 X 18*2 


The groups COOCH s , COOC 2 H 6 have elsewhere been found 
to be equal to 59 0 and 80*9 respectively. The numbers would 
give to 

(COOCH 8 ) 2 the. volume of 2 x 59*0 118*0 A= - o*6 

COOCH 8 

and | the volume of 59*0 + 80*9 139*9 A = - 0*3 

COOC 2 H 5 

(See Appendix 2, p. 264.) 


The Unsaturated Oxygen Compounds. 48 


/- 

Acrolein CH, : CH • CT 

\ 

b.p. 52*4 0*8410 

C = 0*50 \m 69*9* 


H 


Propaldehyde CH S . CH 2 C 


r 

\ 


74*8 


H 


2H 7*4 

CH 8 :CH.c' 67*4 

A = 69*9 - 67*4 = + 2*5. 

There is thus an augmentation due to unsaturation. 

There are no data for acrylic acid, but Weger has studied the 
esters of this acid. 


Methyl acrylate CH 2 : CH . COOCH 8 
b.p. 8o°. Vm 98*6 

CH 8 . CH 2 . COOCH3 104 6 

CH 2 : CH . COOCH, 97*2 

A = 98*6 - 97*2 = + 1*4. 

There is again an increase for unsaturation. 

It is remarkable that a methyl acrylic acid 


ch 2 : c; 


ch 8 


cooh 


Digitized by v^ooQle 



154 


LIQUID CHEMICAL COMPOUNDS. 


should possess a similar volume, viz. 98*4. 


c. 

Unsaturated esters: 
Methyl acrylate, etc. 

Vm. 

Sat. Est. 

-H a = 2 nV a . 

A 

0*515 

CH a : CH . COOCH 8 

98*6 

104*6 (G) 

97*2 

+ i *4 

o *595 

CH, : CH . COOC 2 H 5 

122*0 

128*1 (S) 

120*7 

+ i *3 

o* 55 i 

CH a : CH . COOC 8 H 7 

145*3 

1510 (S) 

143*6 

+ 17 


There is thus seen to be the same augmentation for all these 
compounds. This is considered to be due to unsaturation, or 
rather to the result of an interaction between an unsaturated 
group and an ethenoid linkage. 

The volume of the isomeric allyl acetate 

CH 3 . CO . O . CH a . CH : CH a 
is Vm 121*7. 

Propyl acetate CH 3 . CO . OCH 2 . CH 2 . CH S 

Vm 128*9 
“ H a 7*4 


2»V a 1215 
Vm 121*7 


There is no augmentation in this case, because the ethenoid 
linkage is out of the range of the influence of the unsaturated 


group - 



O 

O- 


It has already been pointed out that the vinyl derivatives 
(p. 88) CH 2 : CHX, etc., show the same augmentation. 


Tiglic aldehyde 

CH S . CH : C(CH 8 ). CHO 
b.p. 116 d 16 0*871 

Vm 109*5 
2CH 8 52*0 
2CH 37*0 
CO 22*2 


111*2 

less for a & -3*1 


108*1 

for unsat. +1*5 

%rNa 109*6 
Vm 109*5 


C = 0*52 


5 c—C-CH 8 \ 

h/ II 


CH—CH 8 / 


Formula of tiglic aldehyde. 


Ethyl angelate 

CH 8 . CH : C(CH„). COOC a H 5 
b.p. 141 do 0*9347 

C 7 H, a O a CH 8 . CH a . CH a . CH a . COOC 2 H 5 (ethyl valerate) 
C =* 0*578 


Digitized by v^ooQle 




ORGANIC COMPOUNDS CONTAINING OXYGEN. 155 

Ethyl angelate V** 163*9 

2CHj 52 


c 2 h b 48 

coo 33*3 

C 2 H 5 OOC-C-CH 3 *, t 

C a H 33-3 


166-6 

CH -CH 8 / 

less for a & struct. - 3*1 

Formula of ethyl angelate. 


163 s 

for unsat. +1*3 

The increase for unsaturation 

— 

is in this case doubtful. This 

2»Va 164*8 

Vm 163*9 

may be due to inaccuracy in 


the calculations. 

Ethyl tiglate (ethyl and methyl crotonate) 

CH, . CH : C(CH 8 ) COOC,H, 

b.p. 152. 

<*o •9425* 

C ass *58 Vw 164*1 

2CH 8 52*0 

CjHj 48*0 

COO 33*3 

C»H 33*3 

C 2 H 5 . OOC—C——CH 8 \^ 


CH—CH 8 / 

166-6 


less for a & struct. - 3*1 

Formula of ethyl tiglate. 

163-5 

for unsat. +1*3 

or 

CH 8 —C—COOC 2 H 5 

2»V fl 164*8 


Vm 164*1 

HC—CH 8 

Ethyl angelate and tiglate are probably isomers of the type 

H \ c . c / cooc » H » 

H W CH * 

CH,/ ' \CH, 

CH,/ \COOC,H, 

The evidence is not quite clear 

as to which formula represents 

the angelic acid derivative and which is the tiglate, owing to 

want of precision in the data. 


The Substituted Esters . 49 

Ethyl monochloracetate 


CH 2 C1 . COOC 2 H B V w 

1239 

CH 8 .COOC 2 H 5 Vm 1061 


less H - 3*7 

H 

I 

102*4 

plus CF 21*5 

Cl—c—c = 0 

2 nVa 123-9 

1 1 

H OC 2 H b 

Vf» 123*9 

Digitized by CjOO^Ic 





LIQUID CHEMICAL COMPOUNDS. 


*5* 


Ethyl dichloracetate 

CHCl,COOC 9 H 5 Vm 143*9 
CH,.COOC 9 H 5 V w io6*i 
less H 9 - 7*4 


98*7 

plus Cl' +215 


120*2 

plus Cl" 23*5 


2»V a 1437 

Vm 143*9 

Ethyl trichloracetate 

CC1 8 . COOC 9 H 5 
CH S . COOC 9 H 5 Vm 1061 
less 3 H -11*1 


950 

plus cr _+21*5 

116*5 

plus Cl" 48*0 (2 x 


2nVa 164*5 
Vm 164*4 


We find among the above compounds, that as the chlorine 
content of the substances increases, the boiling-points are 
diminished and the volumes augmented. 



b.p. 

A. 

Va(Cl). 

CH 9 C1 . COOC 9 H c 

144*5 

13*2 

21*5 

CHCla . COOC a H* 

157*7 

9*4 

22*7 x 2 

CC1 8 . COOC 9 H 5 

167*1 


23*1x3 


This is exactly what was noticed in the chlor-substituted methanes. 

It is not easy to say whether all the chlorine atoms partake 
of the increase, or whether the increase is only operative on the 
additional carbon atoms. An explanation of the fact of increase 
is no doubt of fundamental importance. 

We calculate the following values in order to obtain a broader 
basis of fact:— 


C. 


b. P . 

A. 

^19* 

Vm. 

V(C1) average. 

0*540 

CH 9 C1. COOCH3 

128*5 

i5*5 

1*2352 

100*9 

21*4 

o*555 

CHC1,. COOCHj 

144*0 

7*5 

I*38o8 

120*8 

22*5 X 2 

0*570 

CCI3COOCH3 

152*5 


1*4892 

141*1 

23*0 x 3 


Again, we notice the phenomenon of gradually diminishing 
differences in boiling-points and increasing volumes as the 
number of chlorine atoms increases. The values may be cal¬ 
culated from that of methyl acetate as before. 


Cl" 

I 

Cl—c—c=o 
I I 

H OC„H. 


Vm 163*4 

Cl" 

I 

Cl'—C—COOC 2 H 6 
Cl" 


54*0) 


Digitized by v^ooQle 



ORGANIC COMPOUNDS CONTAINING OXYGEN 157 


Calculated 


Esters. 

2»V a -»H. 

+ »C 1 . 

values. 

Vm. 

CH S . COOCH 8 

83*2 



83*2 

CH S C 1 . COOCH. 

79*5 

21*5 

101.0 

100*9 

CHC 4 . COOCH 8 

75*8 

21*5+23*5 

120*8 

120*8 

CClj . COOCH 8 

72*1 

21*5+48*0 

141*6 

141*1 


A very interesting series of compounds is that of the mono-di 

and tri-chlor acetic acids. 

Monochloracetic acid CH a Cl. COOH 
b.p. 186*0 d n 1*366 (Hoffmann). 

C = 0*530 \ m 78*0 
CH s COOH 640 
less H - 3*7 


plus Cl 

2»Va 

Vm 


60*3 

21*5 

81 *8 
78*0 


We notice in this case a large difference of - 3’8 between the 
two values. On examination we find that this is just what we 
should expect, for on writing the formula 


H 


HX- 


-Cl 


■M 


/ 


Cl 


O: C 


-O . H 


y \ 


we see that the substance is an a /3 chlor-hydrin. 
subject to a contraction of about - 3*1. 
Trichloracetic acid. CCl a . COOH 

b.p. 197*0 (mean) 1*617 


OH 

As such, it is 


C = 0*570 
64*0 


Vm ii.9*5 


3H -ii*i 


Cl' 


2CI" 


less for aft structure 

2«V« 

Vm 


52*9 

21*5 

74*4 

48*0 

122*4 

-3-i 

119*3 

119*5 


Cl 


Cl- 


C 1 

“xl / 3 


</\>H 


Digitized by v^ooQle 




158 LIQUID CHEMICAL COMPOUNDS . 

Since there is only one hydroxyl group it can influence only one 
chlorine atom, and so only the simple contraction — 3*1 is found 
throughout the series. 

The Dibrompropionic Esters . 48 

Weger has determined the volumes of a number of dibrom 
esters, which present some noteworthy features. 

In order to facilitate the investigation we have calculated 
the volumes of the corresponding a dibrom esters. For the 
a /3 dibrom methyl compound C = 0 5 2 5 

CH, . CBr, . COOCHg b.p. 182° d 0 1*9043 Vm 156*3 
Vm I 56 * 3 * 

CH a BrCHBr . COOCH, b.p. 205*8 

Vm 152*4* 

A -3*9 

There is thus a considerable contraction for the a /3 compound as 
compared with the other. 

Starting from methyl propionate we can calculate the result, 
remembering that the volume of an a bromine atom (from acid 
group) is larger than one in the f 3 position with reference to this 
group. 

The f 3 bromine atom which is at the end of a chain only 
possesses a volume of 27*5, whilst one in the af 3 has a larger 
volume, 29*5. 

CH, . CBr a . COOCH, Vm 156 3 
CH 8 . CH a . COOCH, 104*6 

less 2H - 7*4 

97*2 

2 Br" 59*0 (2 x 29*5) 

2nV a 156*2 volume of a compound 
Vm 156*3 

CH a Br . CH . Br . COOCH, Vm 152*4 
CH, . CH a . COOCH, 104*6 

less H a - 7*4 

97*2 

CH9- CH - C = 0 Br' 27*5 

I I I 

Br Br OCH 3 Br 

less for afi struct. 

2 nV a 152*2 
Vm 152*4 



H Br 


H—c—d— c = o 
A L d)CH 3 


Digitized by v^ooQle 



ORGANIC COMPOUNDS CONTAINING OXYGEN . 159 


The contraction - 3*9, already noticed, is made up as 
follows:— 

- 2*0 for ajS struct. 

- 2*0 for A between a and & bromine 

A -4*0 

This may also be shown from an examination of dibrom 
propyl alcohol. 


ch 2 

- Bn 

\ 

1 


1 

1 

/ 

CH- 

I 

- B K 

V 

I 

) 

ch 2 - 

- OH' 


3CH f 66-3 

Br' 27*5 

Br" 29*5 

O' 7*4 


1307 

for ajS struct. - 6*2 

2»V a 124*5 
V m 124*3 

ajS dibrom propionic methyl ester. 

CH 2 Br . CHBr . COOCH s 

CH s Br . CHBr . COOC a H ft 
CH a Br . CHBr . COOC 8 H 7 

The A for CH 2 is thus an unusually large number for com¬ 
pounds like the above. The only explanation is that there is an 
augmentation for complexity. Thus the equivalent volume in 
178 *6 

CH 2 units is ^ y - = 8. We have noticed that compounds of 

the order of complexity of octane (C 8 H 18 ) are subject to augmen¬ 
tations for the above reason. Elsewhere the augmentation per 
CH 2 increase has been shown to be equal to +3*5 in certain 
classes like the esters. Frequently the augmentation starts from 
the methyl ester. 


Vm. A. 

152*3 

26*3 

178*6 

26*0 

204*6 


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160 LIQUID CHEMICAL COMPOUNDS. 


a 

dibrom propionic ethyl ester 



CH, . CBr 2 COOC.,H 5 

Vm 1817 

a/8 

CH a Br . CHBr . COOC 2 H B 

178*6 



A -3*1 


CH S . CH 2 . COOC 2 H b 

1277 


less 2H 

“ 7*4 

Br 



| 


120-3 

ch 3 — c- 

-C = 0 2Br" 

j 

59-0 (2 x 29-5) 

ir 

oc 2 h b 

i 79‘3 

. 

augm. for complex. 

+ 3 5 (1 x 3 * 5 ) 



182*8 


V m 

1817 


CH, . CH 2 . COOC 2 H b 

1277 


less H 2 

- 7*4 

riTT pTT 

n A 


OUo" — vU 

--o 


1 1 

I 

120*3 

1 1 

1 Br ' 

27*5 

Br Br 

OC2H5 

147*8 


Br" 

29*5 



177*3 


less for a/8 struct. 

— 2 *0 



175-3 


augm. for complex. 

+ 3-5 (1 x 3-5) 


2«V a 

178-8 


V w 

I78*6 



' 


CH 2 Br . CHBr . COOC 8 H 7 

204*6 


CH, . CH 2 . COOC,H 7 

149*9 


8 less H 2 

- 7*4 

CHo-CH— 

c=o 


1 1 

I 

142*5 

1 1 

1 Br' + Br" 

57 *o 

Br Br 

V._^ 

OC3H7 

199*5 


less for a/8 struct. 

-2*0 



197-5 , 


augm. for complex. 

+ 7 0 (2 X 3-5) 


2nV a 

204*5 


Vm 

204*6 


It is remarkable that neither the : O nor the OCH, groups 
cause contractions. 


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ORGANIC COMPOUNDS CONTAINING OXYGEN 161 


The Volume of :0 in Union with S, N, and P. 

It has been shown that the volume of : O in union with carbon 
varies from 7*4 to n*o. 

Its volume, when the atoms to which it is attached are N, S, 
P, is however different—uniformly so far as we can see 

DO] - 8-2. 

This is illustrated by a number of compounds which have been 
investigated by Thorpe, but since their full consideration demands 
a knowledge of the volumes of nitrogen, phosphorus, and sulphur, 
this is left till later. We content ourselves at present with one 
or two calculations which do not involve this knowledge. 

POClj 101*4 
PCI, 93-3 

A for : O 8*i 

107*4 
992 

8*2 

S 0 2 C 1 2 863 

S 0 C 1 2 780 

A for : O 8*3 

These results are sufficient to show that the volume of : O in 
these compounds is 8*2. The other cases which involve a know¬ 
ledge of the volumes of nitrogen, phosphorus, and sulphur give 
similar results. 


POBrCLj 

PBrCl a 

A for : O 


The Aromatic Acids. 61 


When the radical C^H 6 replaces the aliphatic radical R, a 
large contraction occurs. 

Benzoic acid. 



\ 

CH 


CH 


CH 


/ 


C 


Vm 126*9 

C 6 H 5 92*8 


COOH 34*i 


- CbOH 


A 


- — 4 ’ 2 * 
II 


c b h u cooh 

Vm 152*4 
C 5 H u 114*1 

COOH 38 3 


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162 LIQUID CHEMICAL COMPOUNDS. 


Phenyl propionic acid and cinnamic acids. 


CH 

CH 


^ \ 

✓ \ 


CH CH 

CH CH 

1 II 


1 11 

CH C—CH,—CH^—COOH 

II 

CH C—CH = 

= CH—COOH 

\ / 

\ / 


CH 

CH 


V w 170*9 

Vm 

162*7 

C # H 5 . CH, . CH, 135*6 

C 6 H 5 . CH : CH 

127*5 

COOH 35*3 

COOH 

35*2 

A = - 3*0 

A = - 3 *i- 

The volumes of the residues C 6 H 6 . CH 2 : CH 

2 . and CjH 6 . 

' : CH . have been obtained as 

follows :— 


Ethyl benzene. 

Cinnamene (styrolene). 

C,H 5 . CH, . CH, 

C 6 H 6 . CH : 

CH, 

Vm I 39'3 

Vm 

131*2 

less H 3*7 

less H 

37 

C 8 H 6 . CH, . CH, 135*6 

C 6 H b . CH : CH 

127-5 

The fact that the two values 

of COOH are 

similar, even 


though the saturated and unsaturated compounds are different in 
constitution, is sufficiently remarkable. 

Styrolene is made up as follows :— 

CgH 8 92*8 
CH : CH 2 407 


2 nVa 133*5 

less for unsat. and assoc, with C 8 H 5 - 2*3 


C 6 H 5 . CH : CH a 1312 

We thus work out the value for cinnamic acid 

C 6 H 5 . CH : CH . COOH 

C 6 H b 92*8 
2CH 37*0 

COOH 38*3 


168*1 

less for unsat. and assoc, with C 6 H S of hydrocarb.CH : CH - 2*3 


165*8 

less for assoc, of C 8 H 6 and COOH - 3*1 

2#V a 1627 
V m 1627 


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ORGANIC COMPOUNDS CONTAINING OXYGEN 163 


These numbers exactly agree. We are, however, met with 
the difficulty of the possibility of interaction between two un¬ 
saturated groups QH 6 and COOH, when these groups are, on 
the basis of the ordinary formula, separated from one another. 

This difficulty can, however, be met by effecting a change in 
this formula, whereby the two groups are brought near each 
other. We may at the same time deal with phenyl propionic 
acid. The suggested formulae for the two compounds are thus 
CH 2 -CH 2 CH = CH 

C 6 H 5 COOH C 6 H 5 COOH 


Phenyl propionic acid. Cinnamic acid. 

A = - 3*0 A = - 31 

c 6 h 5 

CH : CH 

Aooh 

Allocinnamic acid (possibly). 

These results thus agree with those obtained by ordinary 
chemical methods. There is a necessity for at least two modifica- 
ti ons of cinnamic acid on the basis of the modified formulae. 


Aromatic Esters. 

It has been shown that in the aromatic acids the association 
of QH 6 and COOH or other acid radical is responsible for a 
contraction 

a * -3 0. 

In methyl benzoate C,H 5 . COOCH, 

CH 


HCOOCH, 


Vm = 627 
H 37 


59 ‘o 

* This difference may he in part explained by the fact that in methyl formate we 
have the combination H - C - OCH„ in benzoic acid C - C - OCH s . If we compare 
the latter with methyl acetate CH, - CO - OCH, which has a similar grouping , we 

II * 


CH 


x 

CH 


CH C—COOCH, 

\ / 

CH 

V w = 150*3 

CgH 6 92*8 


COOCH, 


57*5 


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164 


LIQUID CHEMICAL COMPOUNDS. 


Ethyl benzoate C 6 H 8 

. COOC a H 8 

HCOOC a H 8 



174*2 

Vtn 

84*6 

c 6 h 8 

92*8 

H 

37 

COOC a H 6 

81*4 


80*9 


A = -*0*5. 


We thus see that the association of C*H 5 and the following 
groups produce the contractions 

A 

rcooH -30 o— c=o 

C 6 H 5 | COOCH 8 -i *5 II 

lCOOC a H 8 -05 R C 6 H 5 . 

The effects just noticed depend 
{a) on the C*H 6 group; 

( b ) on the nature of the R group; 

(c) possibly on the circumstance that the neighbouring 

carbons of the nucleus are unsaturated. 

The group OH by itself occasions a contraction of only 0*8, so 
that the large contraction for benzoic acid must be due to the 
large amount of residual affinity connected with the group 


Amyl benzoate C 6 H 5 . 


c 8 h 5 

co 2 


92-8 

333 

114*1 


240*2 

augm. for complex + 7*0 (2x3 *5) for C 8 - C 4 


5»V a 247*2 
Vmt 247*3 


The hydrocarbon chain of greater length than C 4 occasions an 
expansion of +3*5 for every CH 2 added— 

65 4321 

—C—OCH a . CH a . CH a . CH a . CH 3 
II 

o 

The volume of every member of this group of aromatic esters is 
thus easily calculated. 


find for COOCH, 83*2 - 25*9 = 57*3, which is similar to that for the same group in 
benzoic acid. The volume of this group in ethyl benzoate C 6 H 5 . COOC 9 H 5 is about 
1*5 higher than in methyl benzoate , as it should be 

•COOCHg = . COOC 9 H 8 - CH a = 81*4 - 22 = 59*4. A = + 57*5 - 59*4 = - 1*9. 


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ORGANIC COMPOUNDS CONTAINING OXYGEN. 165 


The Phenyl Propionic Esters. 

CH 

^ \ 

CH CH 

I II 

C C—CH, . CH, COOR 

\ / 

CH 

In synthesizing the values of these compounds we utilize the 
general data:— 

C„H, 92-8 CH, 22-1 CH, 26-0 C,H, 48-0 C,H, 70-0 
The augmentation for complexity above C 4 at A = + 3 ‘°- 

Phenyl propionic propyl ester 

C 6 H 8 . CH 2 . CHj . COOC 3 H 7 
C 6 H 6 92*8 
2CHj 44 ‘2 
CO, 333 
C s H 7 70-0 


2403 

augm. (C 6 - C 4 ) + 6-o (2 x 3*0) 

2»V a 246*3 
Vm 246-0 


Vtn . 

C 6 H 5 . CH 9 . CH 2 . COOCH3 195*2 196-3 

C 6 H 8 . CH 2 . CH a . COOCjH 5 221-5 221*3 

C 6 H 8 . CH a . CH 2 . COOC 8 H 7 246*0 246-3 


A. 

- i-i 


The contraction - ri in the case of the first compound agrees 
with former results. 


The Cinnamic Esters. 

CH 

S \ 

CH CH 

I " 

CH C—CH : CH . COOR 


\ / 

CH 

In these compounds the contraction seems to have disappeared, 
for on utilizing the following data:— 


C 6 H 8 92-8 CH 18-5 COOCH3 59-0 COOC 9 H 8 80-9 COOC 3 H 7 10, 


numbers similar to those obtained by experiment are calculated:— 


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166 LIQUID CHEMICAL COMPOUNDS. 

Cinnamic methyl esters 

C 6 H b . CH : CH . COOCH3 




C-H b . CH : CH 2 

131*3 

C«H 5 

92*8 

less H 

3*7 



2CH 

370 


127*6 

COOCHg 

59 *o 

COOCH, 

59 *o 

SnV a 

188*8 

2»V a 

186*6 

Vm 

188*3 

V m 

1883 



A = 

+ i* 7 h 


There is thus an augmentation of 17 approximately equal to the 
effect for unsaturation. 


Compound. 

V m . 

2»V*. 

A. 

C 6 H 6 . CH : CH . COOCHj 

188*3 

188*8 

-0*5 

C 6 H 6 . CH : CH . COOC 2 H B 

213*75 

213*7 


C 6 H b . CH : CH . COOC 3 H 7 

239*4 

238*8 

— 


Methyl salicylate C 6 H 4 (OH)(COOCH 8 ). 


V m 1567. 

CH X C-OH 


CH ,C- -COOCH3 

T 5 H 

C B H 4 89*6 

COOCHj 59*0 in open-chain compounds. 

OH io*i in alcohols. 


158*7 

for assoc, of OH and C 6 H 6 - 0*8 (see for phenols) 


157*9 

for assoc, of COOCH 8 and C 6 H 6 -1*5 (see for methyl benzoate) 


2nV a 156*4 

V m 1567 


* Such an increase is noted in methyl ethyl and propyl acrylates when compared 
with the same salts of propionic acid :— 


propionate 

A 

acrylate 

OCHj 104*6 

5-9 

98*7 

OC,H, 1277 

57 

122*0 

OC,H, 1510 

5*8 

145*2 

A 

5*8 for H 2 


A = 7*2 

- 5*8 = + i ’4 



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ORGANIC COMPOUNDS CONTAINING OXYGEN. 167 


This is better seen from the following :— 

V m 


C 6 H 6 OH 102*0 
C 6 H r . CO a CH s 150*3 


Sum 252*3 
less for C 6 H 6 - 96*0 


2»V a 156*3 
V m 1567 

The volume of methyl salicylate can thus be accounted for 
without supposing that there is any action between the two 
groups in the ortho-position. That the association of these two 
groups should normally interact is rendered probable by the 
following calculation :— 


0 Cresyl methyl ether. 

-OCH3 


y c \ 

CH C- 


CH .C- 


-ch 3 . 


c 6 h 6 *ch 8 


p cresyl methyl 148*0 

o „ „ 146*4 


A = - i*6 

by summation— 

A = - 1 '3 


125*6 

ii8*3 


Sum 243*9 
less C 6 H 6 —96*0 


147*9 
W m 146*4 


A +i*5 for 0 structure. 


This compound is evidently " adjacent ” 

The only explanation which we can offer is that methyl 
salicylate is an “ opposed compound. 

OH 


CH=CH I 

/ \l 

CH C 

\ ✓ 

. CH-C 


:ooch s 


There is thus an “ adjacent ” modification also possible. A 
number of exceptions to the rule among the different compounds 
have been found, and since it is shown that their volumes do not 
involve any contraction although ortho compounds, we conclude 
that the groups are outside the range of each other's action. This 


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168 


LIQUID CHEMICAL COMPOUNDS. 


occurs under the circumstances that the groups are on opposite sides 
of the nucleus, that is the compounds are “ opposed ” compounds. 


The Volume of Ring Oxygen. 52 

A preliminary study of the subject might lead us to suppose 
that the volume of ring oxygen is invariable. A more minute 
examination of the data shows that this is not so. 

In the first place ring oxygen 



is apparently ethereal in character, and as such might vary, even 
as it does in 


—ch.,— o— ch 3 - ch 2 —o—c 2 H 5 

C 6 Hg—O—CH a . 

Moreover, in certain cases, it is found that ring oxygen, or 
indeed any other combination including oxygen, may be related 
to the volume which it possessed in the original compound 
If we consider such cases as 


CH 2 -CH 2 -OjH 

r J 


GH<2- CH a - 


CH.-CH, 


\ 

/ 


O H 


We see the possibility of ^)0 retaining its volume relative 

to hydrogen in the ring compound. 

A safe rule to follow is to assume the contraction compatible 
with the class of ring we are considering, and then finding the 
volume of oxygen by difference. 

Ethylene oxide C a H O 
V,* 50*0 

CH aX 

I >0 CH„CHO 567 

CH a / 2CH a 44*4 

> O = 12-4 


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ORGANIC COMPOUNDS CONTAINING OXYGEN. 169 

2CH, 44-4 
> O 12-4 

56-8 

less for O3 ring - 6 '° 

5»V a 50*8 
V m 50*0 


CH S —O—CH,. CH . CH S V m 105*1 
less C 4 H 10 96*0 

>0 « 9*i 

2CH 2 44*2 
CH 185 
' Cl 2i*5 

> O 9*i 

93*3 
-6*o 


87-3 

87-3 


Furfurane C 4 H g O Vm 73*2 


CH = CH\ CH 

ch=ch/° 

, . CH a — 0 — 

CH, . CH, 

Vm 

less C 4 Hjq 

106*3 

96*0 


> O 10-3 

4 ch 

74 *o 


>0 

10*3 



843 


less for O5 ring 

- iro 


S«V« 

73*3 


Vm 

73*2 


Furfural C 6 H 4 O a 

Vm 95*7 


CH = C—CHO 

4 CH 

74 *o 

N /° 

>0 

103 

CO 

22*1 

/ 



CH = C 


106*4 

less for 0« ring 

- n*o 


2 «Va 

954 


Vm 

957 


less for Os ring 

2nVa 

Vm 



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LIQUID CHEMICAL COMPOUNDS. 


170 


Citraconic anhydride C B H 4 0 8 
d u 1*2536 (Knops) b.p. 214 

CH S —C-CCK C = 0*46 

II JO Vm 106*4 by formula. 

CH—CO/ 

This compound is a derivative of methyl succinic acid and 

thus we might expect the volume of > O to be 7*4. 

CH a 22*1 
2CH 37*0 
2CO" 52*0 

>0 7-4 


118*5 

less for £7 b r » n S - iro 

2nV a 107*5 
Vm 106*4 


Citraconic and mesaconic acids 
CH 5 —C—COOH 

j 

CH—COOH 


There is probably a contraction 
for the attachment of the group 
CH 8 to an unsaturated system. 

cooh— c— ch 8 

Ih—COOH 


probably both possess similar volumes owing to the fact that 
there are two groups in apposition in the two compounds. The 
theoretical volumes are— 


Citraconic anhydride 106*4 
H 2 0 i 4 *8 


121*2 

less for a)9 struct. - 1*5 


Va 1197 


The whole contraction is -3*1, but seeing that there is an ex¬ 
pansion of +i*5 for the ethenoid link, the resultant contraction 
is only — I * 5 

Butyrolactone C 4 H 6 0 2 

d Q 1*441 (Saytzeff) b.p. 206 
C = 0*46 Vm 90*0 (by form.) 


CHj—CH 2n ^ 
O 

/ 

CH a — CO 


3 ch 8 

66*3 

CO" 

26*0 

>0 

9*6 


101*9 

less for £7 b rin g 

-11*0 

5 mV« 

90*9 

Vm 

90*0 


We have thus the following interesting series of compounds:— 


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ORGANIC COMPOUNDS CONTAINING OXYGEN 171 


CH,—CH,—OH ch 2 CH 2 -jOH CH = CH 


CH a —CH 8 

l 

CHjCOOH 


CH 2 -CH 2 


Ih,- 


-CH, 


ch 2 


\> 

/ 

! CH=CH 

O !H ^ 

1 Ring oxide (ethereal). 


CH a —co x 


CH- 


CH 3 -CO |o H -* I 

j CH,—CO^ 


or 


CH- 
Anhydride. 


CO O | H 


-CO 


-CO 


\ 

/ 


o 


ch 2 — 

■co ;oh] 


CH,—CO v 

I '0 Lactone. 

1 / 

CH 2 - 

i ! 

1 —1 ! 

- 

co o:hi 


CH,—CH, 


In every case the different peculiarities of structure can be stated 
in terms of volume. 


8 Hexylene oxide C 6 H 12 0 


CH,—CH—CH. 

/ \ 

CH, O 

\ / 


d 0 0-8739 

b.p. 104*0 C = 0*46 


CH 2 -CH, W m 129*2 by formula. 


CH, . CH 2 .0 . CH, . CH, . CH, 

c 3 h 7 —0 

—C S H. 

Wm 127*9 

Wm 

151*3 

C|H m 1178 

c«h 14 

139*9 

]> O 10*1 

>0 

ii *4 

6CH, 

132‘b 


>0 

n *4 



144-0 


less for £7e ring 

-15-0 


5 »V a 

129*0 


W m 

129*2 



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172 


LIQUID CHEMICAL COMPOUNDS. 


Diethylene dioxide C 4 H 8 O a 
CH a -CH a 

/ \ 

\ / 

CHj—CH, 


d 0 1*0482 
C = 0*46 

4 ch, 

2>0 


b.p. 102*0 
Vm 94*7 
88*4 

21*0 average 10*5 


less for ring 

SnV a 

V m 


109*4 

-15*0 

94*4 

947 


CH a - 


Camphor C 10 H 16 O 
-CH-CH. 


CH 


a- 


CH, 


CH. 


Ah, 


-C : O 


V m 187*6 

Ci 0 H i 6 2O 7 *2 
: O n*o 


218*2 

less for ring - 30*6 


2»V« *187*6 

Vm 187*6 


CH* 


-CH-CH. 


CH 3 —C—CH S 


CH. 


CH a 


Vm 190*5 

h 18 

O' 6*4 (as in alcohols) 


214*6 


CH OH less f or r j n g _ jQ.g 

S»Va 190*4 

V m 190*5 


Paraldehyde C 6 H ia O a 


CH, 

L 

/ \ 


CH S —CH CH—CH. 

\/ 

O 


v« 151*0 (Schiff). 


C«H„ 133*2 
3 > O 33*0 


166*2 

less for /~~7 fl ring - 15*0 


2 n V a 151*2 
V m 151*0 


Paraldehyde has a similar structure to that of mesitylene. 


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Google 



ORGANIC COMPOUNDS CONTAINING OXYGEN 173 


OH. 


CH a 


CH 

/ \ 

o o 


CHg—CH CH—CHg 

Paraldehyde C 6 H ia 0 3 
V« 151*0 


✓ \ 

CH CH 


CHg—C C—CHg 

CH 

Mesitylene C 6 H 12 C 3 
162*4 


A = -n*4 


The difference in volume should be on the assumption of 
similarity of structure. 

A = 3C - 3O = 3(C - O) = 3(14-8 - n o) 

= 3x3*8 = 11*4 

This difference is identical with the one observed. 


Summary of Chapter on Oxygen. 

Oxygen has been shown to possess quite a number of values, 
according to its position and function. This is in opposition to 
Kopp’s idea that only two values are found :— 

O' = 7*8 O" = 12*0 

The reason doubtless is, that the volume of O and every other 
atom varies somewhat according to its environment. Be¬ 
sides this, we ought to consider the nature of the forces acting, 
that is the residual affinity. An exact notion of these circum¬ 
stances eludes us. All we can do is to tabulate the values, and 
compare them with the known constitutions of the compounds. 
Under favourable circumstances we can draw up a series of rules 
which may act as guides in enabling us to decide on the real 
volume of oxygen in an uninvestigated compound. The inquiry 
has not gone quite far enough to do this with precision. In 
molecular volumes we roughly classify the varying types of 
oxygen as:— 


(a) Hydroxyl oxygen 

O' 

5-6 - 7-4 

(b) Ethereal oxygen 

>0 

9*0 - n*o 

(c) Aldehydic and ketonic 0 " 

7*4 - n*o 

(d) Carboxylic 

0. 

16*4 - 18*0 


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174 


LIQUID CHEMICAL COMPOUNDS 
TABLE LXX. —Values of Oxygen in Organic Compounds. 


O' 


Aliphatic. 

6*4 (in alcohols) 


^>0 (ethereal) 
O" 


7*4 (in esters) or [n*o]* 
9*5 (* n —OCH s ) 

io-ii (in —OR) 


Aromatic, etc. 

5*6 (in phenols) 

7*4 (in esters) or [iro]* 
7*5 (in —OCH s ) 

io-ii (in —OR) 


aldehydic and 
ketonic 
O" 

carboxylic 

°" 

in union with 
S, P, N 


7*4 (aldehydes) 
n*o (ketones) 

ii*o (in acids and esters) or [7*4]* 
8*3 


Ring oxygen as in ethers . 

A requirement of the first importance is to know how the 
volume of oxygen varies according to its position in a chain. In 
some cases the information is definite and complete, in others it 
is very indecisive. 

H—O—R CH 8 —O—R C 2 H 6 —O—R C 4 H 9 —O—R 

Va 6*4 9*6 10 11 


These facts show that the volume of the terminal oxygen is 
always the minimum value, and the volume increases as the 
oxygen passes into the interior of the molecule. 

Similar results are shown in the following:— 

CH S —O—C —R C 2 H 6 —O—C —R C3H7—O—C— R 

II II II 

OOO 


30*6 


32*0 


327 


When the C 0 2 is in the middle of the chain the volume is a 
maximum. Another way of stating the same thing is to suppose 
that the groups CH 3 , C 2 H 6 , C 8 H 7 produce depressing actions on 
the volume in an order which is in the inverse of the order in 
which they are written down. 


CH S . CH a . COOCHg Vtn 104*6 %Na 107*0 A -2*4 

CH 3 . CH 2 . COOC 2 H b 1277 129*1 -1*4 

CH S . CH 2 . COOC 3 H 7 151*0 151*2 — 

That the methyl group is specially concerned in producing a 
contraction is shown by the following— 

CH3.COOCH3 Vm 83*2 SnVa 85*3 -2*1 

Similarly in aromatic compounds there are contractions when 
* See Note on page 176. 


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ORGANIC COMPOUNDS CONTAINING OXYGEN 175 


two CH 3 groups are in the ortho position relative to each other. 
By analogy we have the configurations :— 



av - 2*4 - 2*4 
A b. p. + 2 - 4 + 3 0 . 


An examination will show that the boiling-points of the 
methyl esters are always 2-4 degrees higher than what might be 
expected from the differences. 

For some reason the acids show an augmentation instead of 
a depression, which fact is contrary to expectation. 


Acid. 

v m . 

A. 

Ester. 

V w . 

CH 8 . COOH 

63-9 

+ 1*2 

hcooch 8 

62*7 

C a H B . COOH 

88*4 

+ 3*8 

H . COOC 2 H 6 

84*6 

C 3 H 7 . COOH 

107*9 

+ i *7 

H . COOC 3 H 7 

106*2 

C 4 H 9 . COOH 

130*0 

+ 2*4 

hcooc 4 h 9 

127*6 

C 6 H 9 . COOH 

152*9 

+ 2*4 

HCOOC 5 H n 

150*5 

The reason for this is : 

not known. 




We may also consider the question of the change in volume 
under the following circumstances :— 

CH a (OH) . CH a . CH a . CH a . CH 8 CH 8 . CH(OH). CH 2 . CH 2 . CH 8 

CH 3 . CH, . CH(OH) . CH a . CH 8 

CHO . CH a . CH a . CH a . CH 3 CH 8 . CO . CH a . CH a , CH 5 

CH 3 . CH a . CO . CH a . CH S 

The information on these matters is meagre and inconclusive. 

A general rule seems to be that the volume of a typical atom 
increases as it is placed further from the end of the chain, and 
attains its maximum when it is attached to the central carbon 
atom. Accompanying this is a corresponding depression in the 
boiling-point of the compound. 

As a result of careful examination we think it desirable to 
exclude such general and vague ideas as symmetry, shape, etc., 
as possible influences operative in deciding the volume of a com¬ 
pound, and to substitute more precise notions, as the specific 
actions or influences, due to particular groups. The forces acting 
are doubtless those of residual affinity, and though symmetry, 
etc., are involved, yet it is only indirectly. 

The most probable explanation of the facts, and one which 
is intiipately concerned with the question of what we mean by 
molecular volumes, is as follows: As a result of residual affinity 


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176 


LIQUID CHEMICAL COMPOUNDS. 


arising from the molecule, there is produced an external field of 
strength which may be the sum total of the effects arising from 
individual atoms. This external field causes an intermolecular 
pressure which at once influences the boiling-point and the 
molecular volumes. If the field is relatively great, the boiling- 
point is raised and the volume diminished by compression and 
vice vers&. 

Thus (a) the alcohols are more reactive than the ethers. We 
find relatively high boiling-points and small volumes. The effect 
of an oxygen atom diminishes as it tends towards the middle of 
the chain. 

(b) Similarly when we compare aa with a/8 compounds we 
are comparing the effect of the combinations—CH 2 —CHX 2 and 
—CHX—CH 2 X. As X becomes removed from the end of the 
chain the boiling-point diminishes and the volume increases. 
The two atoms X, however, may also influence one another, and 
by their proximity when attached to different carbon atoms 
intensify each other's action, and thus the external field. This 
would account for the observed increase in boiling-point and 
diminished volume as compared with aa compounds. 

(c) The above considerations also affect ortho compounds as 
compared with para, and from what we have seen the methyl 
esters as compared with ethyl and propyl. 

We should expect to find the capillary constants and viscosity 
coefficients of the high boiling-point compounds relatively high. 
This is what we do find. 


Note. 

Alternative Interpretation of tv a . (0 2 ) = 18 5. 

It has been shown that 0 2 in the esters possesses a volume 

0 2 = 18*5, 

and O" = ii*o, O' = 7*4 (seep. 147), 

which numbers are similar to those indicated by Kopp. 

Whilst this book was passing through the press an alternative 
explanation of the value of 0 2 suggested itself and it has much to 
recommend it. The chief advantage is that thereby a considerably 
greater consistency in theory is secured than by the former ex - 
planation. 


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ORGANIC COMPOUNDS CONTAINING OXYGEN 177 


Thus :— 

O" = 7*4 (as in the aldehydes and ketones and doubly bound oxygen 
generally), 

O ' ^>0 

O' = 9*1 (in methyl esters); g*g (methyl ethers ). 

= n*o (in higher esters) ; 11*0 (higher ethers), 

= 12*0 (in acids). 

The value of O' is similar to that of ethereal oxygen , which from 
a chemical point of view it is. The only difficulty is to account for 
the value O" = n in COCl % and analogous compounds. 

If the above be the true explanation , which we believe it is, 
Kopp's theory, 0 ,f — 12, O' = 7*8, is found to be once again at 
fault. 


12 


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CHAPTER V. 


THE MOLECULAR VOLUMES OF SULPHUR COMPOUNDS. 

The Element Sulphur. 

The molecular volume of sulphur in the uncombined state is 

S = 21*8 Ramsay 52 

and in the combined state 

S| = 21*6 
S, = 25*6 

The first value in the combined state is for doubly bound 
sulphur : S. 

The second value is considered to be the normal one. 

In considering the characteristics of sulphur at, and near the 
boiling-point, we find— 

fusion-point 111-5 yellow mobile liquid 
„ 250*0 dark and thick 

„ 300-0 dark but thin 

boiling-point 440*0 orange-coloured vapour. 

In the liquid state, 

the molecules are probably S 10 and S 8 . 

At any rate in the vapour, the complexity is 

at 500° s # . 

and at iooo° S, 

There is thus dissociation 

S* ? 3S a . 

The formula for S 2 is certainly 

<S = S> 

but the molecule S 8 , so far as we know, has not been explained. 
The formula for S„ must explain at least three facts— 

(a) The existence of colour. 

lb) The easy decomposability of S 8 into 3^. 

(c) An average value of sulphur of 21*8. 

178 


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MOLECULAR VOLUMES OF SULPHUR COMPOUNDS. 179 


The colour phenomenon can be explained on the assump¬ 
tion that the formula for S 6 contains at least three double 
bonds. 

The average value for sulphur of 21*8 can be explained 
either by an open-chain formula or by one which, as a whole or 
in part, involves ring structure. 

The open chain formula would be 

: : 

<s = s = s = s = s = s> 

: : 

j i 

This explains colour and easy decomposability. 

The possibility of this type of formula depends on whether 
sulphur has sufficient power of self combination to form a 
molecule with this length of chain. 

That this may be so is suggested by a formula for potassium 
pentasulphide 

k-s-s-s-s-s-k. 

We must also assume that = S = possesses the volume 
of 21 # 8, if we take and consider the above formula. 

The volume of sulphur in 

o =« s = o 

25*6 is contrary to this idea. 

Possible ring formulae are— 



Average volumes. 

22*5 22*7 21*6 


The only one which gives an average volume similar to the 
experimental one is the third, but should be excluded owing to 
the fact that easy decomposition is not suggested. 

In spite of the fact that the value of S for the first, is slightly 
higher than that indicated by experiment, it seems the most 
satisfactory one. It explains the phenomena of colour and easy 
decomposability. 

12 * 


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i8o 


LIQUID CHEMICAL COMPOUNDS . 


I 



S 

The average volume of sulphur is calculated thus— 


3 atoms of: S 3 x 25*6 

768 

3 „ S 3 x 21*6 

64*8 

6 atoms of S 

141*6 

less for ring 

-6*5 

S« 

I35*i 

s 

22*5 


Probably we do not know all the facts connected with a 
formula of the above type. It is quite possible that there are 
influences which would tend to lower the average value to the 
one given by experiment. 


The Halogen Derivatives of Sulphur (Thorpe, loc. cit.). 

Sulphur di-chloride. 

Cl—S—Cl. 


b.p. 64 


Vm 

S 

2C1 

3«Va 

Vm 


do 1*62 C 0*46 

68*8 (by formula) 

25*6 

43*2 


68*8 

68*8 


Sulphur monochloride. 

Sod, 

Vf n go*3 (Thorpe). 
Two formulae are possible— 

Cl 

/ 


s = s 


\ 


and 


Cl 


Cl 


/ 


1 

Cl' 


The first is the analogue of o « s , and the second is an 
a# compound. 


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MOLECULAR VOLUMES OF SULPHUR COMPOUNDS . 181 


ist formula. 2nd formula. 


/ 


2S 

512 (2 X 

25-6) 

= s 

25*6 

2CI 

43' 2 (2 x 

21*6) 

\ 
= s 

2C1 

21*6 

43*2 

less for ajS str. 

94*4 

-3*1 


2nV a 

90*4 

'ZtNa 

9i # 3 


v w 

90*3 

Vw 

90*3 



A - i*o 


The validity of the first is suggested by the calculations. 
One other compound like the above is 
Sulphur monobromide. 

S 2 Br 2 . 

Br 

/ 

S = S b.p. 170° d 4 2*628 C 0*46 

\ 

Br 



Vw ioo*o 

/ 

= S 

25*6 

\ 

= s 

21*6 

2Br 

54*0 (2 x 27*0) 

5nVa 

101*2 

Vm 

100*0 


The calculations are found to be distinctly in favour of the 
first formula, to which we adhere. 

We possess also the following evidence for the atomic values 
which have been proposed:— 

SC1 2 68*8 
SSCU 90*3 

t S 21*5 


It follows that 
and 



possesses a volume of 25*6 
one of 21 *6 


This is proved by the following results:— 


Cl 

S'V 256 


C 2 H 5 —N = Ct=S 

Vw 99*3 
C,H 6 .N:C> 77-5 


: S 


21*8 


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182 


LIQUID CHEMICAL COMPOUNDS. 


Thorpe has come to the same conclusion, but in a different 
way. Thus:— 


SSCL, Vm 9°*3 

ci. 

45*4 (2 x 227) 

2S 

45*0 (2 X 22*5) 

2nV a 

9°*4 

V w 

90*3 


We have seen that the two sulphur atoms are not equal in 
value, but possess respectively the two volumes characteristic of 
this element Moreover, we have reason to think that the 
chlorine atoms do not possess quite so large a volume as Thorpe 
and, indeed, Kopp supposed. 

Thorpe has investigated a number of compounds which are 
similar to the above, but containing oxygen, and the present 
theory affords valuable evidence as to their structure. The con¬ 
clusions arrived at more than thirty years ago(i88i) are con¬ 
sidered to be invalid They were obtained by means of Kopp’s 
numbers. The latter thought that only two values for oxygen 
are met with, 

O' 7*8 and O" 12-0. 

This is not the case. At any rate, the particular solution of the 
problem arrived at here hinges on the volume of oxygen. 


SCI, 

68*8 

SOCL, 

78*0 

S0C1, 

78*0 

SOjCl, 

86-3 

O" 

92 

O" 

8-3 


Similar volumes are found when oxygen is united to phos¬ 
phorus and nitrogen. 


PCI3 

93*3 

NO« 

32*0 N 

15*6 

POCI3 

101*4 


20 

16*6 

0" 

8*i 

-ir 

3«Va 

32*2 


T ■ IT 

^0 

Vm 

32*0 


The volume of oxygen in thionyl chloride is apparently 
slightly larger than the other value. This is also the case for 
one of the oxygens in sulphuryl chloride and other compounds. 
The reason for this is not very apparent, but it at least explains 
the volume of sulphur dioxide S 0 2 . 


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MOLECULAR VOLUMES OF SULPHUR COMPOUNDS . 183 


so a 

O 

II 

CO 

II 

0 

Vm 

43*9 

= S = 

25*6 

2O" 

18*4 (2 x 9*2) 

3*V« 

44*o 

Vm 

43*9 


If this be so, then the volume for chlorine is 21*6. 

SCI* 68*8 2CI = 68*8 - 25*6 = 43*2. 

Cl 21*6. 

This conclusion may be arrived at in another way— 

S0 2 Cl(OH) 75*05 

SO a Cl = 75 - 10*4 = 64*6 (OH * 6*7 4- 37) 
SO a Cl 3 863 
SO s Cl 64*6 

Cl 217 

Thus— 


S = 25*6 O" = 9*1 and 8*3 

Utilizing these values, we find— 


Cl =■ 21*6 


Thionyl chloride. 

so*C4 

Cl—S^-Cl 


4 


'XtNa 78*0 

Vm 78*0 


Sulphuryl chloride. Sulphuryl chlorhydrate. 

SO a Cl(OH) 


O 

II 

Cl—S—Cl 

II 

o 

86*3 

86*3 


O 

: JL, 

A 

75* 1 

750 


OH 


The latter compound by condensation gives disulphuryl 
chloride 


Cl-S-OlH+HoV-S-Cl = Cl-S-O-S 


O 


' 1 


- ClSO a » C1S0 9 0H—OH 

= 75*0 - io*4^= 64*6. 

The volume of —O— is thus— 

Volume of ClSO a — O—O a SCl 
2C1SO*— 


133*5 

129*2 


-Cl 


4*3 


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184 


LIQUID CHEMICAL COMPOUNDS. 


This is a small value for oxygen, indeed, the smallest value 
known. 

A possible explanation of this lies in the fact that in the 
aromatic hydroxy compounds like phenol C 6 H 6 OH, where OH 
is united to the nucleus C 8 H 5 _, there is a contraction of - 1*4. 

E.g. if C 6 H 5 OH possess the volume 102*0 

and C 6 H 6 „ „ 96*0 

then O' 6*o 

Since O' = 7*4 A is 6*o - 7*4 = - 1*4. 

Now the —O— atom in disulphuryl chloride is joined on 
to two acid groups —S 0 2 C 1 , or, at any rate, to groups pos¬ 
sessing residual affinity. If we deduct 2 x 1 *4 from the normal 
value for this kind of oxygen we obtain the volume 

O = 7*4 - 2*8 = 4*6. 

This number is not very different from that found, 4 3, and thus 
its remarkably small volume may possibly be explained. 

The formulae supported by the molecular volume theory, and 
which are considered to possess doubly bound oxygen, are dif¬ 
ferent to those which Thorpe has proposed, based on the con¬ 
clusion that the oxygen atom is of the hydroxyl type. Such 
formulae would be 

ci-s—o—ci, ci—o—s—o—ci 

Thionyl chloride. Sulphuryl chloride. 

In addition to the fact that the atomic volume of oxygen found, 
in spite of its similarity to the value for one similar to —O—, is 
a doubly bound one, a formula of this type could hardly apply 
to sulphuryl chlorhydrate, for 

Ci—o—s—O—OH 

is extremely improbable. 

The formulae which have been proposed are also more in 
accord with the properties of the compounds and their genetic 
relationships. It should also be observed that they support the 
view that sulphur is tetra and hexavalent in the compounds 
rather than divalent. 

The Sulphur Oxides, Acids, and Ethereal Salts of the Acids. 

These oxides are two in number, S 0 2 and S 0 8 . 

Sulphur dioxide. 

O = S = O. 

Vm 43 * 9 * 


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MOLECULAR VOLUMES OF SULPHUR COMPOUNDS. 185 


Oxygen appears to have the volume 9*2 in this compound 


s 

25*6 

20 

18*4 

SnVa 

44*o 

Vm 

43*9 


This is also seen in thionyl chloride, 

o 


Cl—S—Cl 

Vm 

78*0 

V 

VmSCI 2 

68-8 


: 0 

g-2 


Sulphur trioxide. 

S0 3 . 

This compound possesses a molecular volume but little 
different from that for S 0 2 . There must consequently be a 
considerable contraction. 

Vm 44*3 
S 25*6 
3O 249 


5°*5 
Vm 44*3 

A -6*2 


This contraction is evidently connected with the presence of a 
three-membered single ring. 

The formula to be accorded to this compound is for this 
reason considered to be represented by 


/ 


o 


o = s 


\ 

o 


so that sulphur is tetravalent instead of hexavalent. It is re¬ 
markable that none of the groups S 0 2 , N 0 2 , CO a contain this 
ring. The formulae are 

O = N = O, O = S = O, 0 = 0 = 0, 

and not 


/ 

—N 

\ 


** V. 

/ 

/ 

» —s 

. <C 

\ 

\ 


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i86 


LIQUID CHEMICAL COMPOUNDS. 


b.p. 161 0 


Sulphurous ethyl ether. 

(CjH 5 0 )S 0 . 

^ i*io6 C 0*50 as in (C,H b O)CO 
Vw 146*5 (by formula). 


\ 

s 

/ 


; O 


c 4 h 10 

96*0 

s 

25*6 

30 

24*9 

3 »Va 

146-5 

Vm 

146-5 




o 


Methyl sulphate. 
(CH s O) 2 SO a 

b.p. 


188 0 d 16 1-333 C 

V w ii2*2 by formula. 
2CH 3 52*0 

SO a 42-2 


o* 


18-6 


0*50. 


2»V tt III*8 

V m 112*2 


Ethyl sulphate. 

(C*H 5 0 ) a SO a 

b.p. 208° d ia 1*1837 Vm 155*7 
2nV a 156*8 


Doubly Bound Sulphur. 


Sulphur, as already indicated, has two values. The second 
has just been found to be associated with the ring compounds 
thiophene and methyl pent thiophene. It is also found in the 
thiocarbimides and thiocyanates. 


Compound. 

Vm. 

S. 

Vm. 

The Cyanides. 

CH». S . cn 

78*2 

21*9 

56*3 

CH 3 . CN 

C a H 5 . S . CN 

IOO’I 

21*8 

78*3 

C a H 5 . c . n 

c 6 h 6 . s . cn 

143*4 

21*8 

121*6 

C 6 H 5 . CN 


A similar number is found to be connected with doubly 
bound sulphur. 

If sulphur mono-chloride possess the formula 


/ C1 / C1 

S = S , analogous to O = S 

V, \ 


XI 


Cl 


the volume of : S would be 21*8 (q.v.) whilst that of = would 
be 25 *6. 


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MOLECULAR VOLUMES OF SULPHUR COMPOUNDS. 187 


Phosphorus sulpho chloride. 


/ C1 

S - P—Cl . 

. Vm Ii6*i 

/ Cl 

<P—Clj»3-3 

^C1 

S 22*8 

^Cl 


Carbon bisulphide. . 
S = C = S 
V» 62*1 
C 14*8 

2 ; S 47*2 


SrtV a 62*0 
Vm 62*1 


The reason is probably that 
the volumes of sulphur are 
slightly larger than usual, viz. 
23 6 by analogy with CO a . This 
idea is supported by the value 
found for sulphur in PSC 1 3 22*8. 


Ring Compounds including Sulphur. 


The compounds answering to this description are few in 
number. They are 


CH==CH 




S 


Thiophene C 4 H 4 S M 


V m 85-1 


4 ch 

74*0 

s 

22*0 


96*0 

less for ring 

-11*0 

2nV a 

85*0 

Vm 

85*1 


/ 

CH a 

\ 

CH,-C: 


fi methyl pent thiophene C 6 H 8 S 


V 

S 

/ 


CH 



113°*° 

°*9935 

0*48 like toluene 


Vm 125*9 

C,H 8 118-4 (32 x 37 ) 

S 22*0 


I 4 0*4 

less for £7« -15*0 

2nV« 125*4 

Vm 125*9 


It is noteworthy that sulphur possesses a volume of only 22*0 
in these compounds and not 25*6 as we should expect from a 
study of the thio ethers. This is different from the results 
obtained for oxygen and nitrogen. 


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LIQUID CHEMICAL COMPOUNDS, 


188 


The Thio Alcohols (Mercaptans) and Thio Ethers. 

R—S-—H R—S—R 

The available data are not very numerous, but the conclusions 
are fairly certain. 



The mercaptans. 



Compound. 

v m . 

R. 

S. 

C a H # . S . H 

77*6 

52*0 

25*6 

C 5 H u . S . h 

143*6 

117*8 

25*8 

ch 8 . S . CH- 
c 2 h 5 . S . C 3 H 6 

The thio ethers. 



121*6 

96*0 

25*6 


It is remarkable that the value for sulphur just indicated is 
also found in very dissimilar compounds, which include di-, tetra-, 
and hexavalent sulphur in their composition. 

It may further be remarked that the sulphur atom does not 
seem to exert any special influence on the alkyl radicals, that is, 
in modifying their atomic volumes, as compared with those found 
in the normal paraffins. Moreover, no distinction is discoverable 
between the mercaptans and the thio ethers in regard to their 
molecular volumes. This is quite different from the results 
obtained in the series 



R— 0 —H 

R—O—R 


R—NH 2 

R a =N- 

-R 

S,0C1 4 

b.p. 100 

d 1*656 

C = 0-45 

cn 

rci 


Vm 147 '° 

Cl ts—s- 

1 

2 S = 

51-6 

ClJ 1 

1=0 

4 C1 

88-4 



0 

8-3 



SnVa 

148-3 



Vm 

147-0 



A 

-1*3 for afi structure 


tetrachloracetyl oxide 

V 
2C 
4 C 1 

o 

* a 

Vm 
A 



-3*0 for ajS structure 


This is analogous to 



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MOLECULAR VOLUMES OF SULPHUR COMPOUNDS. 189 


It has been found that there is an increase in volume of + 1 *5 
in —CC 1 : CC 1 —and similar groups, so that the apparent value 
of A is halved. We may suppose that S 2 . may be represented by 

/ \ 

and that sulphur is hexavalent. We do not, however, think that 
this is the case. 


o 


b.p. 179*5 
Cl 

/ 

\ 

Cl 


Selenium Se 
Selenyl chloride. 
SeOCl* 

<*i3 2 ’443 


: Se^ 

.'i 

CL 


C 0*45 

V m 79*0 


27*0 


9*1 see thionyl chloride 
43* 2 


2nV a 79*3 
V» 79*0 


Selenium chloride 


b.p. 169° 
Cl 


/ 

Se — Se 

\ 

Cl 


Se^Clg 
d 17 2*906 



2CI 
- Se 


C 0-45 

V« 91-4 


27*0 

43*2 (2 x 21*6) 
21*6 


Br 


/ 

Se = Se 


\ 

Br 


2 nVa 

91*8 

Vm 

91*4 

Selenium bromide 

SegBr a 


V m 104*8 

.. / 

= Se 

27*0 

\ 

= Se 

21*6 

2Br 

56*0 (2 x 28*0) 


104*6 

Vm 

104*8 


The above three selenium compounds are quite analogous to 
the corresponding sulphur compounds. For the reasons stated 
the formula is 



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190 


LIQUID CHEMICAL COMPOUNDS. 


excluded. Moreover, selenium is perfectly analogous to sulphur 
in possessing two values, as must be the case from the nature of 
the formulae. 


Thus, the first value for Se x is 27*0 S x 25*6 

and the second value for Scj 21*6 S a 21*6 

The second is similar in value to that of sulphur. 


Chromium Cr. 

(Thorpe loc. cit.) 


Not many chromium compounds have been investigated. 
Indeed, the only one is chromyl chloride Cr 0 2 Cl 2 . 


Cl 



Chromyl chloride. 


CrOXL 

Vtn 

88*2 

2CI 

43*2 

2O 

ie-e 

Cr 

28*4 

2»Va 

88*2 

V m 

88*2 


Cl 



Cl 


Chromyl chloride seems perfectly analogous to sulphuryl 
chloride, and chromium differs from sulphur in possessing a 
slightly larger volume. 

S 25*6 Se 27*0 Cr 28*4 

The volume of tellurium is not known, but probably it pos¬ 
sesses one of from 37-0 to 40*0. 



Elements of 

Group 5. 


M.W. 

Vm . 

Oxygen O 

16 

7*4 under and over 



II-I2 

Sulphur S 

32 

21*6 



25*6 

Chromium Cr 

52*5 

28*4 

Selenium Se 

78-9 

27*0 


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CHAPTER VI. 


THE MOLECULAR VOLUMES OF NITROGEN COMPOUNDS. 


THE atom nitrogen, perhaps, not even excepting oxygen, is 
of greatest interest to us, in consequence of its presence in many 
interesting and useful compounds. 

The element nitrogen 
N = N 

Nitrogen being a low boiling-point substance, it may be 
useful to calculate its value by D. Berthelot’s method. 


T c 


127 0 Pc 33 atmos. 

Vm = ii‘i x I27 a 

D 33 x (254 - 78*6) 


Tb.p. 78*6 
= 30 * 9 . 


The observed value is 


Vtn 30*9 = 2 x 15*5. 

Nitrogen, like phosphorus, is typically a trivalent element, 
and if we are to judge from the latter, the direction of its 
valencies when unconstrained are, as in the diagram, along 
the edges of a tetrahedron. 


Cl 



Such a disposition accounts for the possibility of both nitro¬ 
gen and phosphorus functioning as pentavalent elements. On 
comparing the atoms carbon and nitrogen in this respect, we see 
that carbon cannot assume any higher valency than four—it is 
saturated, whilst nitrogen may take on two more valencies—it is 
unsaturated. 

191 


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MOLECULAR VOLUMES OF NITROGEN COMPOUNDS . 193 


It is remarkable that the above value for chlorine is found in 
such compounds as R—Cl and CH 2 C 1 2 . In this, nitrogen 
chloride resembles PBr 3 , that is, it possesses the minimum value 
for the halogen element found in ordinary compounds. The 
volume of bromine in PBr 3 is also that found in the alkyl brom¬ 
ides R—Br. 

The Cyanides or Nitriles. 

R—C = N. 

These compounds belong to the class known as unsaturated, 
and it will be found that the volume of nitrogen in them is 
normal. 

TABLE LXXI.— The Volumes of the Alkyl Cyanides. 


Compound. 

Vm. 

^Va(R). 

CN. 

b.p. 

(CN) 2 .... 

60*4 

— 

30*2 

21*0 

CH3.CN . 

57*3 

26*0 

3 i # 3 

8i*6 

C 2 H 6 . CN . 

78-5 

48*0 

30*5 

98*0 

C 8 H 7 . CN . 

100*0 

70*0 

30*0 

118*5 


Mean value . 

30*5 



The group CN resembles the combination N 2 in its constitu¬ 
tive features, and might thus be expected to show a similar 
volume in the case of combined nitrogen. 

—C = N N = N 

C i N = 14*8 + 15*5 = 30*3. 

It has already been shown that 

N ; N = 30*9 = 2 x 15*5. 

Isomeric with the nitriles, we find the carbylamines or iso¬ 
cyanides. 

R—N = C > 

In these compounds, carbon appears to be diatomic as in 
<C C = O. They will be considered after the amines. 

Cyanic Acid and Esters. 

RCNO. 

The compound is only stable below o°. 

13 


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194 


LIQUID CHEMICAL COMPOUNDS, 


The boiling-points of the esters are 

ethyl isocyanic ester b.p. 6o° 

methyl „ „ „ 44 0 

acid ,, 11 11 

It is concluded that the boiling-point of cyanic acid is be¬ 
tween o° and 2 5 0 . 


d - 20 

1*1558 

do 

1-1400 

dao 

1*1242 by extrapolation 

Vm 38*2 at 20 0 

Vm 377 at o° 

H 

37 

CN 

30-2 

O 

8*3 

2 «V« 

42*2 

Vm 

377 

A 

-4-5 or -4-0 


A contraction of this nature suggests that there is a three- 
membered ring in the molecule of cyanic acid. If we con¬ 
sider the possibilities of the empirical formula HCNO, we find, 
on starting from hydrocyanic acid and the hypothetical acid of 
the carbylamines, that the following scheme may be drawn up. 



In the case of both non-oxygen compounds, the possibilities 
involved include a ring compound. The contraction associated 


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MOLECULAR VOLUMES OF NITROGEN COMPOUNDS . 195 


with so-called cyanic acid would lead us to suppose that it has a 
different structure from that indicated by the ordinary formula 
(marked 11 ). The only possible one, according to the data, is 

H—C = N > 

\/ 

o 

The instability of the compound, and the tendency to modi¬ 
fication, might lead us to suppose that the ring compound is 
transformable into the open chain one and vice versd. When 
however, the hydrogen is replaced by an alkyl group, the latter 
fixes the constitution and the cyanetholins result. The transition 
to the second group of compounds, chief of which are the iso¬ 
cyanates, probably demands and points to an “ intermediate ” 
compound, involving ring structure. This condition is satisfied 
by Formula I for cyanic acid. 

Thio Compounds. 

There are, corresponding to the oxygen compounds, the 
following combinations with sulphur. 

N = C—SH and < S = C = NH 
Thiocyanic acid Isothiocyanic acid 

Sulphocyanic acid Sulphocarbimide. 

Hydrocyanic acid HCN at the boiling-point 27 0 possesses a 
volume of 38-8. 

HCN 38*8 
CN 30-2 

H 8-6 

This enormous volume for hydrogen is what we should 
expect. On this basis the volume of CNSH would be 


HCN 

S 

38*8 

22*0 

HCNS 

60*8 


Clasen gives the density of (^ 0 ) 1-0013 for what is called 
hydrosulphocyanic acid 

or Vm 58 9 

so that we see that the constitution is that of an open-chain 
compound, perhaps HS . C = N. However this may be, thio- 

13 * 


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196 


LIQUID CHEMICAL COMPOUNDS. 


cyanic acid gives rise to esters, which have been well studied, 
and which possess the formula 

N = c— SR 

The hypothetical HN = C = S > has derivatives called 
thiocarbimides R—N =* C = S > 


The sulphocyanides. 


Methyl sulphocyanide. 


Ethyl sulphocyanide. 


cHjS. c : 

N Vm 78*2 

c 2 h 5 s . c 

l N 

ch 8 

26*0 

c 2 h 5 

48*0 

s 

22*0 

s 

22*0 

CN 

30-2 

CN 

30*2 

2nV a 

78*2 

SnV a 

100*2 

Vm 

78*2 

Vm 

100*1 


V m 1001 
b.p. 146 


We see that these compounds give results in perfect accord 
with their formulas. 

Isothiocarbimide CS : NH is not known, but some of its 
esters, the mustard oils, S = C = NR are. 

We only give details of the ethyl ester in this place; the 
others are dealt with after the amines for reasons to be given 
later. 

Ethyl thiocarbimide. 

C 2 H 5 N : C : S b.p. 133° V m 99 3 

Vw 99*3 
2»Va IOO-2 


-0-9 

There is thus a difference of 13 0 between the boiling-points 
of the two isomers, and a difference in volume of 0*9. The 
thiocarbimides possess the lowest boiling-points and the smallest 
volumes. 

The carbylamines give rise to the isocyanates or carbimides. 

Ethyl carbimide C 2 H 6 —N = C = O 

b.p. 6o° di 0 0*8981 C = 0*55 
V m 85*5 

C a H 5 48-0 
CN 30-2 

O 7*4 


2»Va 85-6 
Vm 85*5 by formula 


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MOLECULAR VOLUMES OF NITROGEN COMPOUNDS. 197 


Phenyl carbimide C 7 H„NO 


>.p. 163° d 50 1*092 

C = 0*45 from 

Vm 121*7 

phenylthiocarbimide 

c«h 5 

92*8 

CN 

30*2 

O 

7*3 


130*3 

less for attach, to C 6 H, 

-i *4 

2»V a 

128*9 

Vm 

1217 

A 

-7*2 


Whilst ethyl carbimide is apparently normal, in that it pos¬ 
sesses the open-chain formula, and so all the alkyl carbimides, 
phenyl carbimide, on the other hand, seems to possess abnormal 
structure. 

This is indicated by the large minus difference, and shows 
that there is a three-membered ring in the molecule of phenyl 
carbimide. Such a formula as that indicated in the preceding 
scheme would be suitable. We must then suppose that phenyl 
carbimide possesses the structure shown by the formula 

C 6 H 5 —N — C > 

\/ 

o 

It will be seen that the other aromatic compounds of this 
nature are quite normal. 



TABLE 

LXXII. 




Compounds. 

v m . 

SnVa—R. 

A. 

b.p. 

C. 

C(jH B . c ; n . . . 

121*6 

123*0 

-l* 4 

— 

— 

C,H„ . N : C > . . 

121*7 

123*0 

“ **3 

— 

— 

C„H, . S . C : N . . 

143*4 

145*0 

-1*6 

I 3 i° 

— 

C,H t . N : C : S . . 

143-6 

145*0 

- 1*4 

219*8 

0*45 


Thus there is for the above compounds a contraction of - I *4, 
owing to the attachment of the unsaturated groups to the nucleus. 


The Amines. 

The amines are derived from the cyanides or nitriles by the 
addition of nitrogen. 


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198 


LIQUID CHEMICAL COMPOUNDS. 


There is in the process of reduction a remarkable contraction. 
2 h 2 + c 2 h 8 . c : n c 2 h 5 ch 2 . nh 2 

14-8 78-2 93*o 

The real volume of propyl amine is 

C 8 H 7 NH 2 Vm 85*2 
A = 85*2 - 93*0 = - 7-8. 

Reduction in the cyanides thus produces a contraction. 

The starting-point of the amines is ammonia. 


H 

/ 



N—H 

Vm 

26*9 

\ 

H 

N 

i 5‘8 


3 H 

ii*i 


2nV a 26*9 
V*, 26*9 


This maximum value of nitrogen is preserved in such simple 
compounds as NH S , NC 1 3 , N = N, etc., and in the complex 
tertiary amines, as will be shown. 

In considering the amines we are met with the feature of a 
divided chain. This can be seen from the plane formulae 
ch 3 ch 8 ch 8 



ch 8 


\ / 
N 



There are important points of difference, however, between 
these two classes of compounds. 


TABLE LXXIII.— The Paraffins. 



b.p. 

A. 

V. 

A. 

ch 3 . ch 2 . ch 2 . ch 3 

i° 

-18 

96*0 


CH(CH s ) 8 

-17 




CHg . CH 2 . CH 2 . CH 2 . CH a 

38 

-8 

117*8 

-0*4 

CH 8 . CH a . CH(CH 8 ) 2 

30 

-28 

XI 7"4 


C(CH 8 ) 4 

10 




ch 8 . ch 2 . ch 2 . ch 2 . ch 3 

7 i 

-9 

139-9 

-0*5 

CH 8 . CH 2 . CH a (CH s ) a 

62 

“7 

139-4 


CHg. CH(C 2 H 5 ) 2 

64 

-13 


- 3 *i 

(CHg) a . CH . CH . (CHg) a 

58 

-28 

136*8 

- 1*0 

CHg . CHg . C(CHg)g 

43 

-23 

138*9 



or 48 





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MOLECULAR VOLUMES OF NITROGEN COMPOUNDS. T 9 g 


It is seen that the boiling-point becomes depressed as the 
hydrocarbon chain becomes more and more branched. The 
volume is correspondingly diminished. Additional data are 
however, urgently needed. 

TABLE LXXIV.— The Amines. 



b.p. 

A. 

V. 


H a NC a H, 

18 0 

-10*8 

64*6 


HN(CHJ S 

7*2 




h 2 nc 3 h, 

49 *o 

“ 35*5 

857 

+ 2*3 

N(CH 3 ) 3 

3*5 


88-o 


h s nc 4 h. 

76*0 

— 20*0 

106*8 

+ 2*5 

HN(C 2 H,) 3 

56*0 


109*3 

H 2 N(C,H 13 ) 

130*0 

-41*0 

148*0 

+ 4*6 

N(C 2 H,) s 

89*0 


152*6 



The results of the above table show, that, whilst the boiling- 
points of the two series of compounds diminish as the chain 
becomes branched, the series varies as regards volume. In the 
paraffin series the volumes contract as branching occurs, in the 
amines they expand as a result of this circumstance. In the 
first series, the boiling-points and the volumes vary in the same 
sense, among the amines in opposite senses. This at least 
shows that the boiling-points are not always a guide as to the 
manner in which the volumes will change. We now examine 
the volumes in order to ascertain, if possible, the modes of 
increase. 

We have already made use of the principle of constant rela¬ 
tive volumes, for example, in discussing propyl and allyl alcohols. 
We now apply it to a discussion of the amines. It may be 
stated in passing that, until this principle was applied to this 
group of compounds, the volume relations appeared very perplex¬ 
ing, and the results not very trustworthy. As we shall see by 
its utilization, nearly all the difficulties vanish. 

If we consider propyl and allyl amines, we find 


CH S . CH a . CH 2 NH 2 
CH a : CH . CH 2 NH 2 


V m . 

857 

78*5 


A for H 2 7*2 (2 x 3*6) 


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200 


LIQUID CHEMICAL COMPOUNDS. 


N(C 8 h 7 ), 

N(CjHj), 

222*53 

20070 

6H 

21 83 (6 x 3*638) 


1 

N(CH 3 ), 

88-o 

N(C a H t ), 

152*6 

3CH a 

64*6 

CH, 

21*6 (6 x 3 60) 


We thus notice once again the familiar relations 
CH 2 = 6H C = 4 H H = 3 *6o 

Among the primary amines we also find that the following 
similar value holds. 


Vm. 

C 2 H 8 NH 2 646 
C 3 H 7 NH 2 857 


CH 2 21*1 

The relations already indicated will enable us to ascertain 
the volume of nitrogen in the three series of amines. 


CjHjNHj 

CjHjNH,, 

V m . 

64*6 

857 

2»V a (R). 

54 '° 

75 '® 

N. 

io*6 

10*1 

b.p. 

18 

49 

NH . CjH, 

109*3 

97-2 

12*1 

7*2 

N(CH,), 

N(C 2 H 6 ) s 

88*o 

152*6 

75-6 

r 4°'4 

12*4 

12*2 

3*5 

89 

3CH 2 

SSl 

64*6 

21-53 

222*53 

20070 

207-36 

i 85'54 

15*17 

15*16 

156*5 

155*5 

6H 

H 

2X-83 

3638 





The values are apparently from 10-11 in the primary amines, 
12-15 * n the secondary and tertiary; the volume of the nitrogen 
atoms thus varies in volume in the different compounds. 

There are many peculiarities connected with this series, and 
one of the chief is the unexplained value for nitrogen. The 
most useful point of view in which to regard the amines is to 
compare them with the alcohols and ethers. 


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MOLECULAR VOLUMES OF NITROGEN COMPOUNDS. 

201 

Alcohols. 

CH 3 . CH 2 . CH 2 . CH 2 . OH 

Vm. 

ioi*8 

Primary amines. 

CH 3 . CH 2 . CH 2 . CH 2 . nh 2 

Vm. 

l° 7 * 4 



Secondary amines. 

CH 3 . CH 2 . NH . CH 2 . CH 3 

iog*3 

The ethers. 


Tertiary amines. 

ch 3 


CH 3 . CH 2 . CH 2 . O . ch 3 
ch 3 . ch 2 . O . CH 2 . ch 3 

105*0 

io6*3 

CH 3 . N . CH 2 . CH 3 

CH 3 . N(CH 3 ) 2 + ch 2 

iog*6 


We notice that the amino group (NH 2 ) is similar to the 
hydroxyl (OH) group, in that it occasions the smallest volume, 
when in the terminal position. As oxygen becomes situated more 
and more within the molecule, the volume increases, so with 
nitrogen. Moreover there is an additional increase as nitrogen 
becomes the centre for the attachment of three carbon atoms. 

It becomes more and more evident, as we study the subject, 
that we must suppose the typical atoms O, N, S, etc., to produce 
specific effects * on the hydrocarbon radicals and other groups 
with which they are combined. These result in modifications of 
the individual atomic volumes of such groups, whilst as a rule 
the relative atomic volumes are preserved. Thus we have shown 
that the value V/W measures the volumes of the hydrogen 
atoms or equivalents in the different series. If now we consider 
similar terms of the different series 

ch 3 . ch 2 . ch 2 . CH 3 
ch 3 . ch 2 . ch 2 . CH 2 C 1 
ch 3 . ch 2 . CH 2 . CH 2 I 
CH S . CH a . CH 2 . CH 2 OH 
ch 3 . CH 2 . CH 2 . CH 2 SH 

we shall find different values of V/W. Morever, the shape of the 
different curves may not be quite the same, or they will differ in 
some particular. 

If we take the normal paraffin series as the standard, and 
consider the value of the radicals CH 3 , C 2 H 6 , C 8 H 7 derived 
therefrom as the reference values, we shall, on considering other 
series, sometimes find that those which we have to attribute 
to these groups are different. It may also be true that only 
certain parts of molecules are affected by constitutive influences. 
In any case, we must consider that variations from the normal 
are due to the specific influences of certain atoms or groups, as 

* These influences are not necessarily direct, but in any case the atoms N or O 
or the reactive groups containing them are the causes of such effects. 


CH 3 . CH 2 . O . CH 2 . CH 3 
CH 3 . CH 2 . S . CH 2 . CH 3 
CH 3 . CH 2 . NH . CH 2 . CH 3 


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202 


LIQUID CHEMICAL COMPOUNDS. 


well as to differences of arrangement. The constitutive influences 
in question will affect the volumes and probably the boiling- 
points. These definite statements are the outcome of the work 
done on the nitrogen compounds, especially the amines, and are 
considered to be of the first importance. 

It is seen that the primary amines are considerably diminished 
in volume as compared with the corresponding secondary and 
tertiary compounds. In this they are analogous to the alcohols 
as compared with the alkyl ethers. 

As we have seen, there is a contraction of -7*5 approximately, 
when the cyanides are transformed into the amines by reduction. 

Similarly, there are contractions of - I *5 to - 3*5 when the 
aldehydes and ketones are transformed into primary and second¬ 
ary alcohols by reduction. 

We have considered these diminutions in volume as involving 
only the nitrogen or oxygen atoms, but it is possible that all the 
atoms in the groups 

—OH and —NH a 

may be concerned. In any case the constitutive effects are prob¬ 
ably due to the oxygen and nitrogen atoms respectively. 

The alcohols and the primary amines may also be shown 
to be similar in many other respects, but it may be noted that the 
low relative value of the primary amines and the alcohol is con¬ 
nected with the terminal position of the reactive groups NH 2 and 
OH. 

It is to be remarked that the atomic volumes of nitrogen and 
oxygen both reach a maximum in the simplest compounds, 
become depressed as the complexity increases, and finally reaches 
about the maximum value in complex symmetrical amines and 
ethers respectively. 



Vm . 

0 . 


Vm. 

N. 

H—O—H 

18-5 

II*I 

NH, 

26*9 

15*8 

CH S —O—CH, 

62*1 

10*1 

N(CH 8 ) s 

N(C 8 H 7 ) s 

88*o 

12*4 

Cj|H 7 —0—C 3 H 7 

151*3 

n *4 

222*5 

15*2 

c 4 h„—o-c 4 h„ 

I 97 '® 

n *3 



The volumes of amines with 

iso-groups. 





Vm. 

2«Va(R) - 0*5. 

A. 

b.p. 

(CH s ) 2 CH . 1 

ch 2 nh 2 

106*3 

103*7 

-2*3 

68° 

(CH s ) a . CH . CH a 

. ch 2 nh 2 

127*0 

129*4 

-2*4 

95 ° 


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MOLECULAR VOLUMES OF NITROGEN COMPOUNDS. 203 


There is in this class of compounds a depression of about 
-24. 


Compounds Allied to the Amines. 

Ethylene diamine. 

NH 2 . CH 2 . CH 2 . NH 2 b.p. 116*5° d 0 0*902 
Vm 75 *o 

2CH 2 43*2 (12 x 3*6) 

2NH 2 35*6 ( 2 x 17*8) 


SnVa 7^*8 
Vm 75*0 by formula 

A -3*8 

The large contraction which has been associated with a /3 
compounds is here again evident. 

The formula is 

CH 2 -NH >v 

1 ' 

CH 2 -NH^ 

or 



and the contraction is an expression of the effect due to the con¬ 
tiguity of the NH 2 groups. 

Propylene diamine C S H 6 (NH 2 ) 2 



b.p. 120° 

d 1B 0*878 

C = 0*50 

CHo-CH- 



Vm 95*5 

1 


c 3 h 6 

64*8 (3 X 21*6) 

1 

j 

2NH 2 

35*6 (2 x 17*8] 

CEL - 

-Nil' 



2 

a 

2nVa 

100*4 



Vm 

95*5 



A 

-4*9 


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204 


LIQUID CHEMICAL COMPOUNDS, 


Pentylene diamine C 5 H 10 (NH 2 ) 2 


CH,—CH,—NH. 

b.p. 179 0 

d# 0-9174 

/ 

ch 2 

Vm 

134*4 

\ 

ch 2 —ch 2 —nh 2 

c 5 h 10 

io8*o 


2NH 2 

35-6 


2nVa 

143-6 


Vm 

* 34*4 


A 

- 9*2 


From these calculations we see that there are large contrac¬ 
tions connected with a/8, ay, aS, etc., compounds. These have 
been considered in the main to be due to a curvature of the hydro¬ 
carbon chains, owing to the close approximation of the two 
amino groups. 

That this is so, is shown by a possibility of the formation of 
ring compounds from the diamines. For instance, by the splitting 
off of ammonia, the rings become closed and the cyclic alkylene 
imides are formed. 

CH a — ch 2 —nh 2 ch 2 —ch 2 

/ / \ 

CH 2 -> CH 2 NH + NH S 

\ \ / 

ch 2 —ch 2 —nh 2 ch 2 —ch 2 

It is doubtful, however, if the whole of the contractions 
shown above are due to a curvature of the chain. 


Dimethylene compounds 

CH,X, 

A= - 3 ’i 

Trimethylene „ 

CjHjXj 

A = - 4*5 

Then in pentamethylene ,, 

' CjHjdX,' 

A = -( 3 -I + 3 x ** 5 ) 


= - 7*5 


The following is a study of the ring compounds pyrrolidene 
C 4 H 9 N and pipiridene C 5 H n N, which are derived from the 
diamines. 


Tetramethylene diamine 
and pentamethylene diamine 
Pyrrolidene C 4 H 9 N 

CH,-CH 2 b.p. 86-8 

\ 

^,NH 


C 4 H 8 (NH 2 ) 2 

C b H 10 (NH 2 ) 2 

do 0-879 
Vm 90*0 


C = 0*48 


CH* 


-CH a 


We now compare the contractions ob¬ 
tained on the basis of the values H = 3*7 and 3*6 respectively. 


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MOLECULAR VOLUMES OF NITROGEN COMPOUNDS. 205 


4 CH a 

88*4 (4 x 22*1) 

4 CH a 

86*4 (4 X 21 * 6 ) 

N 

12*0 

N 

12*0 

H 

3*6 

H 

3-6 


104*0 

2 nVa 

102*0 

Vm 

90*0 

Vm 

90*0 

A for O5 

-14*0 

A for Os 

- 12*0 


Pipiridene C 5 H n N 

V*» 108*8 (Schiff) 


sC $ 

108*0 

12*0 

CH 2 -ch 2 

/ \ 

H 

36 

CH 2 NH 

'XtN a 

123*6 

\ / 

Vm 

108*8 

CH 2 -CH 2 

A for Oe 

-14*8 


The calculation for pyrrolidene which shows a value of 12 is 
the correct one, since it contains a five-membered ring. From 
this we see that in the diamines the volume of CH 2 = 21*6 and 
not 22*1. 

Thiophene C 4 H 4 S Benzene C 6 H 6 

CH 


CH=CH 


/ % 

CH CH 


CH 



CH CH 


\ ✓ 


CH 


V m 85*0 

(Schiff). 

Vm 

96*0 

4CH 

74-0 (4 x 18-5) 

6CH 

111*0 

S 

22*0 



*nV a 

96*0 



Vm 

85*0 

Vm 

96*0 

A for Os 

- 11*0 

A for Oe 

-15*0 


These numbers agree with those found on the basis of the 
diminished values of V/W or the hydrogen equivalent. This 
rule apparently does not apply to the unsaturated ring com¬ 
pounds. 


Pyrrol C 4 H 5 N 


CH-CH 


CH CH 

\ / 

NH 


b.p. 131 0 
dws 0*9752 
C = 0*46 


Pyridene C 5 H 5 N 
CH 

^ \ 

CH CH 


CH CH 

\ / 

N 


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206 LIQUID CHEMICAL COMPOUNDS. 



V* 79-4 

Vm io8‘8 

(Schiff) 


C 4 H 4 750 

c 5 h # 

92*5 


H 

36 




N 12*0 

N 

12*0 


90*6 


104*5 

for Os -n*o 

less for 0« 

-150 

2 hV u 79*6 

2*V a 

89*5 


V» 79-4 

Vm 

-a 

89*5 



Methyl glyoxylin 

c 4 h,n 2 


C 

:h ( 

:h 

b.p. 199 0 dj. 

1-0363 





C = 0-46 

l 

H 


V*. 

93*8 


\ / 


C.H. 

81-4 


c 

1 


N 

24-0 


ch 8 



105*4 




less for Os 

-11*0 





94*4 


V w 93*8 


CH 


CH 


Quinolene C 8 H 7 N 
CH CH 


CH C CH 

^ \ / \ 

CH C CH 

I 11 1 

1 11 1 

CH C CH 

CH Cl CH 

\ /\ ✓ 

\ /’\ S 

CH CH 

CH N 

Vm 147*2 

Vm 140*0 

Ci 0 H 8 177*6 (48 x 3-7) 

C 8 H 7 159-1 

N 12-0 

less for ring - 30-4 

2»V a 147*2 

171*1 

V m 147*2 

less for ring - 30*4 


2nV a 140*7 

V m 140-0 


A few additional ring compounds will be dealt with at the 
end of the present chapter. 

It will be observed that we have found a value for nitrogen 
similar to those derived from the secondary and tertiary amines. 
This is analogous to the results obtained for rings including 
oxygen and the volume of this atom was found to be similar to 
the values derived from the ethers. We find in this fact one 
more analogy between the amines and the ethers. 

We now turn our attention to another class of compounds, 
the carbylamines, the isocyanates, and the thiocarbimides. 


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MOLECULAR VOLUMES OF NITROGEN COMPOUNDS . 207 


It will be noticed that they all have one feature in common. 

Carbylamines R—N = C > 

Isocyanates R—N = C = O 

Thiocarbimides R—N = C = S 

This feature is, that the alkyl groups are in every case attached 
to nitrogen. They may thus be regarded as derivatives of the 
amines. As such, the alkyl groups are likely to suffer the con¬ 
tractions already noticed, these being due to the interaction with 
the atom nitrogen, that is, CH 2 = 21-6 and not 22*i. 

In order to facilitate comparisons, we give in the following 
table, not only members of the series just indicated, but also 
those of the isomeric compounds in which the alkyl groups are 
attached to the carbon or sulphur atoms. 


TABLE LXXV. 


Cyanides. 

R.C : N 

b.p. 

Vm. 

A. 

V*. 

b.p. 

Carbylamines. 

R—N : C > 

C 2 H 5 . C : N 

0 

o> 

78*4 

- 1*2 

77*2 

79 *o° 

C 2 H 5 . N : C > 

Cyanates 
or cyanetholens. 

R.O.C ; N 
C 2 H 5 .0 . C : N 

0 

0 

5 »Va. 

86*9 

-i *3 

v w . 

85*6 

CT> 

O 

0 

Isocyanates. 

R . N : C : 0 
C 2 H 5 . N : C : 0 

Thiocyanates 
or sulphocyanides. 
R.S.C : N 
C,H fi . S . C : N 

146° 

V m . 

100*1 

-o*8 

Vm. 

99*3 

* 33 ° 

Thiocarbimides. 
R . N : C : S 
C 2 H fi . N : C : S 

C 8 H 5 . S . C i N 

161 0 

115*0 

-i *7 

ii 3*3 

150*7° 

C s H fi . N : C : S 

C 5 H u . S . C : N 

— 

166*5 

-27 

163*8 

182*0° 

C 5 H n . N : C : S 


It is seen that the compounds which possess the 

R—N = 


group have lower boiling-points, and consistently smaller 
volumes. Contractions are thus found which increase as the 
alkyl groups become more complex. As before indicated, this is 
probably due to specific actions of the nitrogen atoms on the 
radicals. The validity of this rule is shown in the following table. 

TABLE LXXVI. 

H 3-6 CH 2 21*6 


Compound. 

Vm. 

N : C > 

+ R 

5 nVa. 

C 2 H b . N : C > 

77*2 

30*2 

N : C : 0 

46*8 

77 *o 

C 2 H 6 . N : C : O 

85*6* 

37*6 

N : C : S 

»» 

84*4 

C 2 H 5 . N : C : S 

99*3 

52*4 

»» 

99*2 

C 8 H 5 . N : C : S 

H 3*3 

»> 

6 i*2 

113*6 

C 6 H u . N : C : S 

163*8 

»» 

111*6 

164*0 


* The volume of this compound agrees better with the usual value of C 2 H 5 48 
S»V a 48*0 + 37*6 = 85*6. 


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208 


LIQUID CHEMICAL COMPOUNDS. 


Aromatic Amino Compounds. 

The interesting subject of the possible mutual influence of 
the phenyl (C 6 H 6 ) and amino groups is capable of fairly extended 
treatment, owing to the extended material which is available. 
It will be necessary to give detailed calculations in order to illus¬ 
trate the methods of calculation. The calculation of values by 
the direct summation of the individual atomic volumes is not 
advisable when compounds of some complexity are dealt with, 
but comparisons with closely analogous compounds are pre¬ 
ferable. 

We first compare aniline and picolene, both of which possess 
the empirical formula C 6 H 7 N, but which possess somewhat 
different molecular volumes. 


Aniline C 6 H R NH 2 


a Picolene 


V m io6*6 


V m 111*7 


CH CH 


CH 


✓ \ 

CH CH 


C 


H CH 

^c^nh 2 


CH C- 

\ / 

N 


-CH, 


C 6 H 5 928 


88*8 

NH a 17-8 

26*0 

iio*6 

N 

12*0 

less for const. - 4*0 


126*8 

less for £7« 

-15*0 

io6*6 


-- 

Vm 106 *6 


in-8 

' 

Vm 

iii*7 


It is seen that there is a contraction of - 4 0 connected 
with aniline. This is in accord with the rule that when an 
unsaturated group is attached to the phenyl radical, there are 
contractions of greater or lesser magnitude. We now investigate 
a number of compounds similar to aniline, but containing hydro¬ 
carbon radicals of different magnitudes. 


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MOLECULAR VOLUMES OF NITROGEN COMPOUNDS. 209 


p Toluidine 

C 6 H 4 (CH 3 )(NH 2 ) 

b.p. 201*5 V m 128*9 
(Neubeck) 



CgH 4 89*6 

CH 8 25*5 

NH 2 17*8 


132*9 

less for const. - 4*0 


2 nVa 128*9 
Vm 128*9 


Benzylamine 

C 6 H 4 CH 2 NH 2 

b.p. 183 d 14 o*ggo 

V m 127*4 

CH 

✓ \ 

CH CH 


CH CH 

\ / 

C-CHjNHj 


l’S: 

92*8 

21*6 

nh 2 

17*8 


132*2 

less for const. 

-4*0 

2»Va 

128*2 

V m 

127*4 


The boiling-point of Neubeck’s compound has been taken 
as 201*5°, but at 198° (the boiling-point usually given), benzyl- 
amine has the same volume as p toluidine. 


CH 

✓ \ 

CH CH 


CH C—NH—NH« 


\ / 

CH 


d 22 1 *091 b.p. 241 0 C *a 0*45 
Vm 120*0 


c 6 h 6 

92*8 

NH 

14*2 

nh 2 

17*9 


124*9 

less for const. 

-4*0 

2 *V a 

120*9 

Vm 120*0 


From this we conclude that the contractions due to the com¬ 
bination of - CH 2 NH 2 with the phenyl radical QH 5 is about the 
same in value as for NH 2 . 


14 


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210 


LIQUID CHEMICAL COMPOUNDS, 


Dimethyl aniline. 
\ m 152*4 


,CH 


CH 


CH 


CH 


CH / CH 3 

C^-N v 

-..-'V 


n ch 


C,H„ 

N(CH,) t 

less for const. 
2nVa 


3 

92*8 

62*8 


Ethyl aniline. 
HC 2 H 
151*6 


Vi 

CH 

/• \ 

CH CH 


CH CH 

\ / 

C-NH(C 2 H 5 ) 


155-6 
-4-0 

151-6 
151*6 ethyl aniline 
152*4 dimethyl aniline 


N(C cife 

N(CHj), 


88*o 

25*2 

62*8 


Dipropyl aniline. 
/C,H, 

c,H 5 r / 


\c,h 7 


N(C c H fl > 

C 8 H 7 08 3 

N(C s H 7 ) 2 154*2 


CjH 5 92*8 
N (CjH,), X 54-2 


less for const. - 4*0 


Diallyl aniline. 
C.H* 


/^J n 5 

C ‘ H ‘ N \c,h 




N(C 8 H 6 ) # 200*7 
C.H. 61*2 


C 6 H 5 92*8 
N(C 8 H 6 ) 2 1395 


2470 N(C 8 H 6 ) 2 139*5 


232*3 


less for const. - 4*0 


S»Va 243*0 
Vf» 243*6 


2»V a 228*3 
V« 2257 


- 2*6 


Di-isopropyl aniline. 
C 6 H 5 N{CH(CH 8 ) 2 } 2 
V#» 235*9 

Di-propyl aniline C 6 H B N(C 8 H 7 ) a 243*6 

Di-isopropyl aniline C 6 H 6 N(C 8 H 7 ) 2 235*9 

A -77 


It is concluded from the above investigation that there is a 
contraction of about - 4*0, when the amino or similar radical 
becomes attached to the benzene nucleus. Moreover it does not 
apparently matter what the complexity of the substituting hydro¬ 
carbon group or groups is, so long as they are saturated. If 


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MOLECULAR VOLUMES OF NITROGEN COMPOUNDS. 211 

unsaturated, in the sense of possessing residual affinity, it seems 
that the contractions are increased. On this last point, however, 
we need further information. 

One very interesting point is, that if methylene groups be 
interposed between the unsaturated radical and the nucleus, it 
makes no difference to the contraction. We have a sufficient 
number of instances of this to be certain on this point. 


p Cresol. 

Vtn. 

Vm-SnV*. 

V*. 

Benzyl alcohol. 

C 6 H 5 (CH s )(OH) 

1237 

“i *3 

123*7 

C 6 H 8 CH 2 OH 

C 6 H 5 . O . CHg 

125*2 



Benzyl chloride. 

2 nVa 

134-9 

-1*6 

i 36*5 

C 6 H 5 CH 2 C 1 





not 





Benzilidene chloride. 

5 »V a 

154*5 

— 

154*7 

C 8 H 5 CHC 1 2 

Benzpic acid + 2CH 2 




Phenyl propionic acid. 

C 6 H 5 . COOH + 2CH. 

170*9 

“ 3*8 

170*9 

C 6 H 5 . CH 2 . CH 2 . COOH 

p Toluidene. 




Benzylamine. 

C«H 4 (CHj)NH 2 

128*4 

-4*0 

127*9 

C 8 H 5 CH 2 NH 2 


It is difficult to understand why this should be so, unless by 
a suitable arrangement of the atoms the phenyl and unsaturated 
groups are brought into proximity. This is probable. Since the 
amount of the contraction apparently bears some relation to the 
reactivity of the groups or the number of unsaturated atoms, we 
must connect these contractions with the residual affinity associated 
with the unsaturated atoms, that is, with the latent valencies. 

We now discuss a number of cases showing interference be¬ 
tween contiguous groups. 


p Toluidene. 

c^-ch 3 

CH 


CH 


CH CH 
"C^NH Q 


b.p. 

198° 

V» i28*g 


2 n V a 128*9 


The Toluidenes. 

m Toluidene. 


*ch 


CH 


X 


-CH. 


CH 


_ CH 

^ C -^ H 2 

b.p. 

199 0 

i*i . 127*8 


A -2*2 

between 0 and p. 
14 * 


0 Toluidene. 


,CH 


CH 


CH 

X 


X 

c- 


-CH 


A 


C-NH 


2 


CH" 


b.p. 

197 0 

126*7 


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212 


LIQUID CHEMICAL COMPOUNDS . 

The ethyl amido benzenes. 


para. 


CH 


ortho. 


% 


c 2 h 6 


*C ET¬ 


CH 




■C 2 H 6 - v 


CH CH 


NH 0 


b.p. 2i6° 

Vm I49 *o # 


b.p. 2i6° 
147*7 


A -1*3 


153*9 


C,H 4 

89*6 

less for const. 

-40 

C s H 6 

4^5 

less for 0 struct. 

149*9 

-2*2 

NHj 

17*8 

153*9 

2nV« 

v w 

't- 

H M 



The Xylidenes. 


1 : 

3 : 4 

1 : 3 

: 5 


CH CH 


CH X C 

V/ 


ch 3 


,c^ch 3 

CH CH 


-CH 3 - n 

\ 

NH 2 "' 


b.p. 

218° 


V_x 

Vm 148*6 (Neubeck) 


ch 3 — 


b.p. 

220 


c— nh 2 


CH 


d 16 0*972 C = 0*52 


CeH, 

2CH, 

NH a 


less for const 

less for 0 struct. 

2 nVa 

Vm 


86*4 

51*0 

17*8 

155*2 

- 4 *o 

151*2 

- 2*2 


I 4 9*0 

148*6 


Vm 151*2 
NH» 


less for const. 

2 nVa 

Vm 


86*4 

5 i*o 

17*8 

155*2 

- 4 *o 

151*2 

151*2 


* The m and even p compounds probably suffer appreciable contractions. 


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MOLECULAR VOLUMES OF NITROGEN COMPOUNDS. 213 

The Oxides and Esters of the Nitrogen Acids. 

Nitrous oxides. 

N 2 0 . 

This compound boils at the comparatively low temperature 
of 186° A. 

Its volume at the boiling-point can be calculated by D. 
Berthelot’s formula from the critical data. 


M 

D 


Vm 


ii*iT 2 c 


P c (2T c - T)’ 

P c , T c crit press, and temperature. T boiling-point temp. 


Compound. 

T. 

D. 

T k . 

P K (atmos.) V w = 

V. calc. 

n 2 

78*6 

0*885 

127 

33 *o 

31*6 

30*9 

NH, 

274*0 

0*635 

403 

115*0 

26*9 

29*5 

n 2 o 

183*0 

— 

309 

73*6 


33 *i 


Vm for N a O is 33*1 

2N 31*6 (2 x 15*8) 

O 8*3 


2nV a 

Vm 


39*9 

33-i 


A = -6*8 


This large difference between the theoretical and experi¬ 
mental values points to ring structure. On considering the type 
of ring which would be suitable, we find that it is compatible with 
a three-membered single ring. Thus 


<N 


N> 

/ 

<N 

This is indeed the only type of structure which is in agree¬ 
ment with our conception of the valency relations of the atoms 
nitrogen and oxygen. It is the only one which would take into 
account the well-known trivalent nature of the one atom and 
divalency of the other. 

This result is of extreme importance in accounting for the 
constitution of the phosphorus oxides. 

Nitric oxide 
NO 


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214 LIQUID CHEMICAL COMPOUNDS, 

The critical data for this compound are 

T c i8o°A P c 71 atmos. Tb.p. i20°A. 
By D. Berthelot’s formula 

v~ = M _ ii*i x 180 x 180 359600 _ ot . o 

m D = 71 X (360 - 120) ” 17040 = 1 

The theoretical volume would be 

N 15*6 
O 8-2 


2nV a 23‘8 


The difference is not too great for this kind of calculation. 


Nitrosyl chloride. 

O = N - Cl 

The data for this compound are 

d-15 1*425 b.p. -5*0° C = 0*46 


Vm 46*7 


N 

15*6 

O 

8*3 

Cl 

22*1 

2 w V a 

46-0 

Vm 

467 


Theory and experiment are seen to agree quite well, and 
also that the divergence from the theoretical value noted in the 
case of nitric oxide NO, is due to the particular method of 
calculating it. 

We are also certain that the true volume of NO is 

NOCl 467 
Cl 22*1 


NO 24*6 

5»V a 23*8 


Moreover the formula for nitrosyl chloride cannot be any 
other than 


o = N—Cl. 


Nitrogen trioxide. 

n,o 8 


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MOLECULAR VOLUMES OF NITROGEN COMPOUNDS. 215 


Data:— 


d 0 1*449 b.p. 4 0 
d 4 1*437 
V» 53*9 

N a 31*6 (2 x 15*8) 
3O 24*9 (3 x 8*3) 


2«V a 56*5 
Vw 53*9 

A -2*6 


It is seen that a difference of 2*9 exists between theory and 
experiment This is not sufficient for us to suppose that there 
is any great modification in structure from the usual one, but in 
attempting to find an explanation we notice one remarkable 
fact, that the sum of the volumes of N 0 2 and NO are almost 
exactly equal to the experimentally derived volume. In the 
latter case, however, we must use the volume found by D. 
Berthelot’s formula and not the one agreeing with theory. 


NOn 

NO 


32*0 ( v . ante) 
23*8 


2»Va 54*8 
Vm 53*6 


This would lead us to suppose that the liquid at 0°, or only 
four degrees below the point at which it vaporizes and is sup¬ 
posed to decompose, is really a mixture of the two liquids NO 
and N0 2 , a supposition which may quite well turn out to be true. 

The formation and decomposition would thus be 


O 


N > + O N = O 


/ 

—> 


\ 


\ 

N >+ 0 

N 


N = O 
/ v 
H-o 


O = N = O 

V 

& = 0 


Possibly all of the above compounds may exist at some 
temperature or another, and no doubt together in greater or less 
proportions. 

Nitrogen tetroxide 
N 2 0 4 

This compound has been actually examined by Thorpe at the 
boiling-point, and the volume found by him was 


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2l6 


LIQUID CHEMICAL COMPOUNDS . 

Vm 64*0 very approx. (63*95 exactly) at the boiling-point 21*6 

NL 31*2 (2 x 15*6) 

0 33*2 (4 x 8*3) 

64*4 
V» 64*0 


In considering the question of structure we might be led to 
suppose that its constitution is represented by 

o o 

II II 

N-N 


This is especially the case if we note that the volume of the 
nitro group in the nitro paraffins is half the volume of N 2 0 4 or 
320. 


C ’ H $: 


80*4 

48*0 


NO, 


32*4 


Certain observations like the following have led chemists to 
suppose that it has a different formula. 

2 NO } 0 + H ,0 = O + 2NO a . OH 

This is indicated by the one just given, which is— 

O 

ll 

N—O—N « O 
II 

O 

or a mixture of the oxides of nitrous and nitric acid. This is 
quite compatible with the molecular volume found by Thorpe 

for NO 24*1 from NOC 1 . 

NO« 32*0 from value in nitro paraffins. 

O 8*3 


2 tNa 64*4 
V m 64*0 


The nitro paraffins. 

V m . 2»V a . 
CH S . NO a 59*6 58*0 


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MOLECULAR VOLUMES OF NITROGEN COMPOUNDS . 217 


The volume of the methyl compound in any series is usually 
larger than that calculated. 

c 2 h 8 no 2 v 80-4. 

This has already been calculated 

C 2 h 6 48*0 
NO a 32*0 


%Na 8o*o 
V m 80-4 

The general formula applicable to these compounds is 

O 

/ 

not K—N 

The esters of nitrous acid. 

Vm* b.p. 

ethyl nitrite C 2 H 8 —O—N = O 7g*2 + 16 0 

If we suppose that the oxygen atom in the C 2 H 6 —O— group 
possesses a similar volume to that found in the esters of the 
carboxylic acids, we obtain the following results :— 

C 2 H 5 48 *o 

o 7-4 
NO 23*9 


79*3 
Vm 79*2 

The formula is that already given. 

R—O—N = O 

It would be advantageous to possess a larger series of values. 

An examination and comparison of the boiling-points shows 
how large a difference exists between the isomers in this respect. 

Ethyl nitrite. b.p. nitro ethane. b.p. 

C 2 H 5 —O—N = O 16 0 C 2 H 8 —N0 2 114-5 

There is no less a difference than 100 degrees between the 
boiling-points. In spite of this fact the law of additivity holds. 
There is also the great probability of the nitro paraffins being 
associated. 


O 

II 

R—N 

II 

O 


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2 iS LIQUID CHEMICAL COMPOUNDS. 

The formation of nitrous acid would be represented thus 


H O = 
H O 
H O 


>N 


H 


c 

I— O 


H O 

H O 
H O, 

H O 


V 


\ * 


-OH 


-OH 


H 0 = N/ OH 

Water then splits off 

H --^N—OH = HO—N = O 

h\o/ 

We have no knowledge of the volume of nitrogen pentoxide 
but its formula is doubtless 

o = N = o 

i 


O = N = O 


United with water this gives 

Nitric acid HNO s . 
d 0 i*54 b.p. 86. C = 45°-o 
V« 45*o 
N0 2 32*0 

HO n*o 


5nV a 43*o 
Vw 45*0 

The excess of V TO over 2 n V a is due to the unusually large 

volume of hydrogen which is found in such compounds. Compare 

HCN! HCl etc. 

The esters of nitric acid. 

Vm. b.p. 

Amyl nitrate C B H n —O—N0 2 152*9 (Schiff) 147 0 


c 5 h u 

114*1 

0 

7*4 

no 2 

32*0 

2nVa 

153*5 

Vm 

152*9 


Again the volume of the oxygen atom in 

R—o 

is found to be 7 4 as in the carboxylic esters and acids, 


Digitized by 


Google 


MOLECULAR VOLUMES OF NITROGEN COMPOUNDS . 219 

The question now arises whether the constitution of the 
remaining group NO a is— 

o 

II 

—N or —0—N = O 

II 

O 

Presumably the formula suited to the nitrates is— 

o 

II 

R—O—N 

II 

O 

but there is difference of opinion with reference to nitric acid. 

Bruhl, 54 from optical data, finds that nitric acid may have a 
peroxide formula 

H—o—O—N = o 

but supposes that the formula represents only one phase of a 
cycle of changes, of which the formula H—O—NO g may be 
another. Klason and Carlson apparently confirm this view by 
the detection of the alkyl peroxide in the products of saponifica¬ 
tion of the alkyl nitrates. 

From our present point of view, we may say that there is 
little or nothing in the way of evidence either for or against this 
view, since it is probable that the volume of HNO s obtained 
would fit either formula. The reason is that the volume of 
the singly bound oxygen attached to nitrogen may not be very 
different from 8*3, the volume of: O. 

The Aromatic Nitro Compounds. 

It has been shown that when unsaturated groups are attached 
to the benzene nucleus, there are considerable contractions. 

We have seen that the group N 0 2 possesses a volume of 
32*0 units when attached to the alkyl radicals and also in N 2 0 4 . 

O 

✓ 

and O = N—O—N 

\ 

If, however, the hydrogen atoms in the methyl group be 
substituted by chlorine atoms, the conditions are realized for that 



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220 LIQUID CHEMICAL COMPOUNDS. 

interaction between the two groups which might be responsible 
for a contraction. 

Chloropicrin. 

Cl O 


II 


CHCl, 

84*5 

Cl C N 

i, 1 

Vm 110*5 (Thorpe). 

CC1, 

8o*8 

H 

37 

no 2 

32*0 

CC1 3 

8o*8 

S*Va 

112*8 



Vm 

110*5 



A 

-2*3 


The operating influences are probably derived from the 
nitrogen atom rather than from the doubly-bound oxygen. 

Contractions like the above are shown when the nitro group 
is united to the benzene nucleus. 


Nitro benzene C ft H s NO a 
b.p. 208° db.p. 1*0073 
V m 122*1 


^ CH \ 

CH CH 



CH CH 


CH 


cn 


b.p. para 

144-8 

238 '- 

2»Va 144-4 


C,H, 928 

NO, 32*0 

2nV a 124*8 

Vm 1221 


A - 2*7 for constitution. 


The nitro toluenes. 


,CH 


CH 


<?H 


\ 


CH 

•z:, 


•CH, 


N0 o 


meta 

144-6 


.CH 


CH 


\ 

C-CH 


3v 


H 0.—NO, 

. 

ortho 

143*0 


-i*8 


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MOLECULAR VOLUMES OF NITROGEN COMPOUNDS. 221 

Orthonitro toluene. 

c 6 h 4 

89*6 

no 2 

32*0 

ch 8 

25*8 


147*1 

less for N 0 2 

- 2*7 


144*4 • • • volume of paramtro toluene 

less for 0 struct. 

-1*8 

2wV fl 

142*6 • . . volume of orthonitro toluene 

Vm 

I 43 *° 


1 

Nitro metaxylene C 6 H 8 (CH 8 ) 2 N 0 2 (1:3:4) 


b.p. 244 0 db.p. 0*9163 
V m 164*8 


CH 


OH 


-CH„ 

X 3 

CH 




C — CH, 


no 2 


C 6 H 8 

2 dH 8 

86*4 

5 i*o 

no 2 

32*0 


169-4 

less for N0 2 

-27 


166*7 

less for 0 struct. 

-i*8 

2nVa 

164-9 

Vm 

164*8 


Nitroortho xylene C 6 H 8 (CH 8 ) 2 N 0 2 (1:2:3) 
b.p. 252 db.p. 0*926 Vm 163*0 

c«h 3 

*CHj 
NO, 



less for N 0 2 
less for 0 struct. 

less for o struct. 

Va 

Vm 


86*4 

51*0 

32*0 

169*4 

169*0 

-27 

166*3 

-i*8 


164*5 

-i*8 


162*7 

163*0 


One or two more ring compounds may now be studied. They 
are interesting owing to the fact that they are either alkaloids 
or connected with alkaloids. 


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222 


LIQUID CHEMICAL COMPOUNDS ,. 


CH 2 

/ \ 

CH CH« 


For propyl benzene 
C 8 H 6 . C s H 7 C ss 0*50 
Coniine 

d 1B 0*850 b.p. 167° 
V m 175*6 by formula 

The most direct method of calculation is as follows:— 


t„ i 


H--CH,—CH,—CH, 


Pipiridene 


C * 


2«V« 

Vm 


108*8 

66*3 

175*1 

1756 


Nicotine c,„h m n s 


N 

^ \ 

CH CH N(CH,) 

I II / \ 

CH C—CH CH, 

\ / 

CH 


—vuj 

Jh,—Ah, 


b.p. 247 0 d 4 1-033 

d 15 i*oi 1 C =» 0*46 

V m 193*1 by formula 

Pyridene 89*3 

Methyl pyrrolidin 110*4 

199*7 

less 2H - 6*4 

2nV a 193*3 

Vm I93*i 


Tropilidene C 8 H 18 N 




do 0*9665 

b.p. 162° C 

= 0*46 

CH,-CH— 

—c 

:h 2 

Vm 149 


Ah 



c 8 h 13 

166*5 

| 



N 

12*0 

CH 





1 




178-5 

k(CH a )-CH— 

—1 

k 

less for ring 

-30-0 




InVa 

1485 




Vm 

149-0 


The above remarkable series of ring compounds indicates 
how closely the theory of molecular volumes is able to synthesize 
the values found by experiment or by calculation by an independ¬ 
ent method. 


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CHAPTER VII. 


THE MOLECULAR VOLUMES OF PHOSPHORUS COMPOUNDS. 


The Element Phosphorus. 

The element has a very much smaller volume in the free than in 
the combined state. 


P = 20*9 (Ramsay and Masson) free 
P = 27*0 combined 


be 


The complexity of the phosphorus molecule is well known to 

P 4 . 


It follows that the molecular volumes are— 


P 4 (free) 83*6 

Equivalent P 4 (combined) 108*0 


A - 24*4 

This is a. large contraction which can only be accounted for 
by supposing that the phosphorus molecule involves ring struc¬ 
ture of a complicated kind. This is difficult to understand, if we 
consider the nature of this molecule. The simplest assumption, 
consistent with the valency relations of the phosphorus atom is— 

P-P 

>-P 

but this would account for a contraction of only -8*5. A modi¬ 
fication of the above 


P-p 



P-p 


which is equivalent to four three-membered single rings is found 

223 


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224 LIQUID CHEMICAL COMPOUNDS . 

to be suitable. Such a configuration would possess a contrac¬ 
tion of 

4 x -6-o = -24*0 

and this is practically the same as the number just found. 

The above formula can be modified in a very interesting and 
suggestive manner, which is shown in the following diagram. 



This represents a regular tetrahedron, with an atom of 
phosphorus at each comer, and the valency linkages directed 
along the edges of this tetrahedron. 

Such a formula explains many facts connected with the com¬ 
binations of this atom, and also of that of the very similar 
nitrogen. 

The valency directions of the single atom of either element 
would be as in the diagram 



N itrogen. Phosphorus. 


and the formulae for the chlorides, etc., represented by 



From the point of view of their spatial relations, these 
formulae at least allow of union with additional atoms, to form 
compounds which involve pentavalent nitrogen or phosphorus. 



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VOLUMES OF PHOSPHORUS COMPOUNDS. 


225 


The molecule nitrogen would be represented by 



or by a modified formula. 

In giving the configurations of certain simple phosphorus 
combinations, we assume that a molecule of phosphorus P 2 (like 
N 2 ) is at least theoretically possible, and rely on certain observa¬ 
tions on the molecular volumes of nitrogen compounds, and on 
the recognized empirical formulae of others, for evidence concern¬ 
ing the genetic relations of the series of phosphorus compounds. 


N 


N 

Elementary 

nitrogen 


P P 

I + 


Simple phosphorus 
(not known) 


N 


\ 


0 


N 

Hyponitrous 

oxide 


+ 


'o 



Phosphorus 

sub-oxide 


N = 0 N = 0 

i\ v \ 

O or o 

n<=o n=o 

Nitrogen trioxide. 

15 


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226 


LIQUID CHEMICAL COMPOUNDS. 



Phosphorus oxide 


The formulae for hyponitrous oxide and nitrogen trioxide 
have been verified by means of molecular volumes. We see 
from the above formulae that similar simple compounds occur 
for phosphorus as for nitrogen but by simple combinations the 
more complex compounds are found to be possible. The 
molecular volume of phosphorus oxide might easily be found 
experimentally. Failing direct data, we calculate the volume of 
this compound by means of the formula already used. 



O 

o 


4P 

108*0 (4 x 27*0) 

PCI, 

93*34 

60 

48*0 (6 x 8*o) 

P 0 C 1 , 

ioi*37 


156*0 

0= 

8*o 

less for O4 

-8*5 




147*5 



less for 2 /~l ? 

“i 3 *o 



2«Va 

134*5 




dj 5 1*936 b.p. 173*1° C = 0*50 
V OT 132*5 

The difference between the two numbers V m and 2 n Va is 
comparatively small. At any rate, it is satisfactory to find that 
there is ample evidence for a large contraction due to more or 
less complicated ring structure. (A = - 23*5 as against - 21*5.) 

Thorpe has determined the volumes of a number of phosphorus 
compounds experimentally, and this not only enables us to find 
the atomic volumes, but also to give the probable structural 
formulae of the different compounds. 


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VOLUMES OF PHOSPHORUS COMPOUNDS. 


227 


Cl 

1 

Phosphorus trichloride. 

PC1 8 

' Vm 93*3 

<P—Cl 

1 

P 

27*0 

Cl 

3C1 

66 *o 


2nVa 

Vm 

93*o 

93*3 

Cl 

1 

Phosphorus oxychloride. 

POCI 3 Vm 10137 

u 

J- 

II 

PCI, 

93*o 

Cl 

0 

8*3 


2nV a 

Vm 

101*3 

101*4 


Cl 

:-L 

i, 


Cl 


Phosphorus sulphochloride. 
PSC1 3 V m n6*i 

P 27*0 


CL 


66*o 


2 „V a 

Vm 


115*0 

ii6*i 


Phenyl phosphochloride. 
C.H^Clg 


X 


C6H5- 


Br 

■P—Br 

L 


Cl 

1 

V m 1617 


. 1 

-p> 

1 

c.h 5 

PC 1 2 

92*8 

71*0 

1 

Cl 

less for const. 

163*8 


— 2*0 


2«V a 

161*8 


Vm 

1617 


Phosphorus tri-bromide. 

PBr s 



Bromine appears to have a similar volume 
to that of phosphorus. 

Vm 108 *3 
108*0 (4 x 27*0) 

IS * 


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228 LIQUID CHEMICAL COMPOUNDS. 

Prideaux has given the volume of PC 1 6 and PBr 5 

Phosphorus pentachloride. 

PC1 8 Vm 128*9 

PC1 5 128*9 

PCI, 93'3 

2C1 35-6 

Cl 17-8 

Phosphorus pentabromide. 

PBr, V m 157-3 

PBr, i57'3 

PBr 3 108*3 

2Br 49*0 

Br 245 


The usual volumes of the two atoms in question are 

Cl 21*6 and Br 27*0 

so that there are contractions amounting to 

Aj = 17*8-21*6 = - 3*8^ 

[per additional atom. 

A* = 24*5 “27*o - - 3 * 5 J 

These are nearly equal values and they represent total con¬ 
tractions of 

-7*6 and -7*0 respectively. 

If the formulae of the compounds are respectively 



it is difficult to understand why the apparent volumes of the 
additional atoms should be so small. The obvious conclusion is, 
that the atoms attached by the two additional valency linkages, 
possess volumes which are smaller than those attached by the 
three others, unless some other explanation is available. 

Against this view, apparently, are the compounds 


Cl 

Cl—P=0 

I 

ci 


Cl 



i, 


Cl 

Cl—p=s 

I 

Cl 


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VOLUMES OF PHOSPHORUS COMPOUNDS. 


229 


from chemical evidence for the volumes of oxygen and sulphur 
are those which we might expect. 

0 = 8*3 S = 22*0 

It follows that in the above respect, the two bromine and 
chlorine atoms are exceptional, if this be the correct view of the 
matter. Why this should be so is not evident. 

One significant fact is, that although the atoms chlorine and 
bromine are different in volume, the contractions are about the 
same. 

This might lead us to suppose that the explanation is, that 
the volume of phosphorus is smaller in these pentavalent com¬ 
pounds than in the trivalent and other pentavalent compounds. 
We have, however, no good ground for supposing that an atom 
with its five valencies acting is notably different in volume from 
that which is true when it only exercises its trivalent function. 

For example, 

Nitrogen trivalent. 

<N=~N> 

Vm 31*6 = 2 x 15*8 

Cl—N=0 

V m 46*8 2«V a 46*0 

N x 15*6 

Phosphorus trivalent. 

Cl 

<lCci 

^Cl 

Vm 93*3 2«Va 93*3 
P 27*0 

Similar relations have been made out for sulphur, and it has 
been shown that S , S iv , and S vi have precisely the same 
volume. 

The conclusion is that the volume of pentavalent nitrogen 


Nitrogen pentavalent. 
O 

/• 

CjH b —N 

\ 

o 

Vm 80*4 8 o*2 

N 15*6 

O 

C 5 H n —O—N 

\ 

O 

Vm 152*9 2nV« 153*5 
N 15*6 O' 7*4 

Phosphorus pentavalent. 
OCH 3 
/ 

0=P—OCH, 

\ 

OCH, 

Vm 1397 2»V a 138-2 
P 27-0 O 8-3 


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LIQUID CHEMICAL COMPOUNDS . 


230 

and phosphorus possess similar volumes to the trivalent atoms. 
The contractions for PC1 5 and PBr 6 are thus not caused by the 
pentavalency of phosphorus. 

The diminution in volume is thus due to the two additional 
chlorine and bromine atoms. 

It may be supposed that the compounds PC1 5 and PB1 5 involve 
ring structure, the latent valencies of the two additional atoms 
becoming active. 

Thus the constitutive formulae of PC1 6 and PBr 5 might be 




This would also explain why there should be a contraction 
in the above instances, and not in the case of 

Cl 

Cl—P=0 and 

/ 

Cl 

The contractions - 7*3 (mean) are not inconsistent with this 
supposition, since O s = - 6 * 5 . 

The only remaining explanation apparently is that phosphorus 
in its action on the halogens, operates differently in the case of 
the additional atoms, than on the three ordinary ones. There 
are however no adequate reasons for this, that is from the stand¬ 
point of molecular volumes. 


ci 

\ 

Cl— P=S 

/ 

Cl 


Thorpe, in his discussion of the series of compounds already 
mentioned, supposed that phosphorus was invariably trivalent, 
and that the constitutions were 

Cl 

<v 

t, 

We have seen that this is not the case, viz. that phosphorus 
is pentavalent. The constitutional formulae are those which 
have been given. 


Cl 

:L 


S. Cl 


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VOLUMES OF PHOSPHORUS COMPOUNDS. 


231 


Only one or two more compounds remain for investigation. 
They are 


Trimethyl orthophosphate. 

OCHj (CH, 0 ) s P 0 

0 =P—OCH a V w 1397 

OCHo P 27*0 

O" 8*3 
3O' 103 0 (3 x 8*3) 


S*Va 138*3 
V« 1397 


o 


OCH s 
k-oc, 

l>CH. 


see that 


Dimethyl ethyl orthophosphate. 

PC 4 H n 0 4 

V m i6i*8 

Comparing the above two compounds we 


its normal value. 


CH a — 22*1 


C a H„ 

< P—C,H 5 
i a H» 


Triethyl phosphine. 

PC 6 H 15 d 0*812 b.p. 127*5 C 0*55 

P 27*0 Vm 170*8 

3C a H 5 144*° 

S»V a 171*0 
Vm 170*8 


The value of C was calculated from the preceding compound. 
No data for ring compounds including phosphorus are avail¬ 
able. In all the compounds studied the atomic volume of 
phosphorus is the same. 

P 27*0 

We have thus found the following atomic values 

N 15*6 N (aminic) 12 and over 
P 27*0 

There yet remain the following triatomic atoms to be con¬ 
sidered— 


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232 


LIQUID CHEMICAL COMPOUNDS . 


Arsenic As 


Arsenious chloride As Cl 3 


fCl 

As 4 Cl 

Vm 94*4 (Thorpe). 

Cl 


As 

27*8 


3 d 

66*3 


5»V a 

94 ' 1 


Vm 

94'4 


Arsenious fluoride. As F s 

V« 53*8 (Thorpe). 

As 27*8 
3F 26*1 (3x87) 


2nV a 53*9 
Vm 53*8 


<F 
As-! F 

If 


Arsenic possesses a volume of only 27*8 in the above 
compounds. 

What its normal value is we cannot say, probably about 30*5. 

Antimony Sb 

Antimony trichloride. 

f C1 

Sb\ Cl SbCl s V m 1007 (Pierre). 

lei 

Sb 34*2 
Cl 3 66*6 


2nVa 100*8 
Vm 100*7 


Antimony tribromide. 

f Br 

Sb-c Br SbBr 3 

IBr 

Sb 34*2 

3 Br 82*5 (3 x 27*5) 

2»V a 1167 
Vm ii6*8 


The atoms of this group thus possess the following atomic 
volumes. 


Atomic Volumes of Group 5. 


Nitrogen (N) 15*6) A 

Phosphorus (P) 27*0 11*4=3 x 3*8 


Arsenic (As) 
Antimony (Sb) 


27*8 

34*2 


V 


2 = 2 


x 3*6 


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VOLUMES OF PHOSPHORUS COMPOUNDS. 


233 


Elements of Group 4. 

Carbon C. 

The question of the atomic volume of carbon has been 
exhaustively treated. 

It has always been found that the volume of carbon is 

C 14*8 

at the boiling-point, or a similar one. 

If the additive rule were strictly followed, it would no doubt 
be shown that carbon has a smaller volume in such compounds 
or groups as 


CH, 


CH, 


ch 3 —i— ch 3 ch 3 —C— 

than is usually the case, but we prefer to consider any differences 
of this nature as being due to constitutive influences possibly 
affecting the whole molecule. 


Silicon Si. 


Si 


Silicon tetrachloride. 


Cl 

SiCl 4 

Vm 120*8 

Cl 

Si 

32*0 

Cl 

4 C 1 

88*8 

k Cl 

— 


5 «Va 

120*8 


Vm 

120*8 


Siiicon tetrabromide. 

Br 

SiBr 4 

V m 144*3 

Br 

Si 

32*0 

Br 

Br 

112*0 (4 X 28*o) 

Br 

2«V« 

I 44'° 


Vm 

r 44"3 


Vanadium V. 
fCl 


f C1 

'{§ 

|ci 


Vanadium tetrachloride. 

VC 1 4 

d 0 1*8584 b.p. 154° C 0*48 
Vm 120*8 
V 32*0 

4 C 1 88*8 


2nV a 

Vm 


120*8 

120*8 


Vanadium oxychloride. 
VOCU 


fd 

V m 

106*3 

=v\ Cl 

V' 

32*0 

lei 

O" 

8*3 


4 C 1 

66*6 


2wVa 

106*9 


Vm 

106*3 


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*34 


LIQUID CHEMICAL COMPOUNDS. 


Titanium tetrachloride. 


III A 1 

Cl 

Vm 

124*47 

Cl 

Ti 

357 

Cl 

Cl 

4 C 1 

88*8 

2»V a 

124*5 


Vm 

124*5 


GermaniunrGe 


Ge 


Cl 

Cl 

Cl 

IC1 


Germanium tetrachloride. 
GeCl 4 

b.p. 86*o d 18 1*887 C 0*48 


Ge 

34*5 

4 C 1 

88*8 


123*3 

Vm 

123*3 


Tin Sn 


Tin tetrachloride. 


Sn 


Cl 

Vm 

i 3 x*i 

Sn 

42*3 

Cl 

4 C 1 

88*8 

Cl 

- 

Cl 

2nV a 

131*1 


Vm 

Elements of Group 4. 

131*1 


Vanadium (V) 51. 

V w 32. 



M.W. 

Vm. 

Carbon (C) 

11*0 

14*8 

Silicon (Si) 

Titanium (Ti) 

28*0 

48*0 

32*0 

357 

Germanium (Ge) 

72*3 

34*9 

Tin (Sn) 

n8*o 

42*3 


Compound. 

BoBr 3 

BoCl s 

Z»(CH 3 ) a 

Ztt(C 2 H 5 ) a 


Miscellaneous Elements. 
V». less n Va. 

102*9 - 3 x 27*5 
87*0 - 3 X 22*0 

72*0 - 2 X 26*0 
Il6*7 - 2 X 48*0 


Bo 20*4 
21*0 
Mean 20*7 
Zn 20*0 
20*7 
Mean 20*4 


Note. —It will be noted that the atomic volumes of the elements in Group 4 can 
be arranged on a regular curve (see Fig. 9, p. 236). The same applies to the elements 
of the other groups. Some are notably out of place. For example As should have an 
atomic volume of 33 instead of 27 which it is found to possess , and which is similar 
to the volumes of Se and Br. I with a volume of 37 is also out of place t and should 
possess one of 32. It thus appears that certain unknown disturbing influences exist 
which may cause the atomic volumes to be modified. An attempt has been made by 
a study of organo metallic derivatives to solve this difficulty. Whilst in certain 
cases the expected values have been found , in others the disturbing influences are 
again apparent. As has been found to possess in some compounds its true volume. 
It is at present impossible to arrive at any definite conclusion till all such compounds 
have been investigated. In spite of these disturbances the periodic relation noted 
can be traced from a general study of the elements. 


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CHAPTER VIII. 


SUMMARY OF THE THEORY OF MOLECULAR VOLUMES. 

A. The Additive Principle. 

This feature, which characterizes most physical properties, is 
very prominent in molecular volumes, although not, as Kopp 
thought, unqualified. This being so, it is essential that accurate 
atomic volumes should be found, at least in so far as this can be 
done with a property in which the influence of the homologous 
increment is felt even from compound to compound in a series. 
The numbers determined by Kopp were, for the most part, in¬ 
accurate, chiefly because the values for the fundamental atoms 
carbon and hydrogen were altogether wrong. 

The values which have been found for the various elements 
in this treatise have been shown to be true, and it is believed 
that they are so, for the reason that by their use many con¬ 
stitutive effects have been revealed and a fairly consistent theory 
built up. As regards the series of values, we have come to 
the same conclusion as Thorpe, even though he utilized Kopp’s 
system in his investigations, that there is a periodic relation to be 
traced between them. This periodic relation has been more 
clearly shown by means of the new theory. The characteristic 
volumes of most of the metals cannot be ascertained at present, 
but those of the greater number of the non-metals have been 
calculated. The following table shows the periodic relation 
indicated:— 

The Periodic Relations Between the Atomic Volumes and Atomic 
Weights Respectively. 

Groups. 

i. 2. 3. 4. 5. 6. 

H — — — — — 

MW. 1 — — — — — 

V« 37 - - - - 

235 



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236 


LIQUID CHEMICAL COMPOUNDS . 


Li. 

Be. 

Bo. 

C. 

N. 

0 . 

F. 

7 

9 

11 

12 

14 

16 

19 

— 

— 

20*5 

14*8 

12*0 \ 

7 * 4 \ 

8*7 





15*6/ 

12*0 J 


Na. 

Mg. 

Al. 

Si. 

P. 

S. 

Cl. 

23 

24*3 

27 

28*3 

3 i 

32 

35*5 




32*0 

27 

2I*6\ 

25*6/ 

22*1 

K. 

Ca. 

Sc. 

Ti. 

V. 

Cr. 

Mn. 

39*0 

40*0 

44 

48*0 

5 i 

52*5 

54 * 8 

— 

— 

— 

35 7 

32*0 

27*4 

— 

Cu. 

Zn. 

Ga. 

Ge. 

As. 

Se. 

Br. 

63*2 

65 

70 

72 

75 

79 

80 

— 

20 

*~ 

35 *i 

27 

27 

27-8*5 

Ag. 

Cd. 


Sn. 

Sb. 

Tfc 

I. 

1077 

1117 

113*6 

n8*8 

ng*6 

125 

126*5 

— 

— 


42*0 

[ 34 * 3 ] 


37 *o 

Au. 

Hg. 

Tl. 

Pb. 

Bi. 

_ 

_ 

1967 

200 

203*7 

206*4 

207*3 

— 

— 

— 

19 *o 

— 

46-5 \ 

48*0 




50*1 



In the following table and diagram we include all the in¬ 
formation regarding the atomic volumes of the elements and 
their relations with each other, which has been obtained by 
means of a study of the molecular volumes of chemical com¬ 
pounds. 


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SUMMARY , OF THEORY OF MOLECULAR VOLUMES. 237 


We see 

(a) That there is a periodic retation between the atomic volumes 
of the elements. 

(b) There is a tendency for the atomic volumes to diminish in 
each series as the atoms increase in weight. The smallest occur at 
group seven. 

(c) There is a general increase in the atomic volumes of the 
members of each group from series one onwards , that is , in the 
direction of increasing atomic weight. This increase is usually 3*6 
or some multiple thereof. 


Variations in the Volumes of the Atoms. 


This important subject has already been dealt with but we 
here give a summary of the results arrived at. In considering 
the variations in the atomic volumes we must distinguish between 
the general causes of variation involved when the homologous 
increment CH 2 is added, and those special influences which affect 
the volumes of individual atoms or, at least, groups of atoms. It 
is difficult to separate them. 

Carbon and Hydrogen .—These atoms do not vary in volume 
except by reason of increase in complexity when the homologous 
increment CH 2 is added. For this reason they vary in each 
homologous series, and also if we compare the volumes of 
hydrogen in corresponding members of different series we also 
find differences 


H 

3-68i 

3*671 

3*647 


These differences may be considered to be due respectively to 
the influence of the typical atoms or groups in each series 


—H, —I, —COO— and so on. 


The latter are influenced by the complexity of the compounds 
as well as those of the hydrocarbon chain generally. 

In practice it is unnecessary to consider small variations of this 
character, except in special cases. Thus carbon and hydrogen 
give the average values of 

C = 14*8 H = 370. 

and these values may be used for all ordinary compounds. 


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238 LIQUID CHEMICAL COMPOUNDS. 

Oxygen O. 

The element is difficult to deal with since it varies to a con¬ 
siderable extent owing to special constitutive influences, and 
shows so many different values. 

The influence of H and CH 8 is such, that, when in combina¬ 
tion with oxygen, the volume of O is reduced to perhaps its 
smallest value. 


The various volumes of oxygen. 


O' 


O" 

>0 


"in the OH group (alcohols and phenols) 
„ „ (acids) 

in the ethers— 

" —OCH. group 

—OR 

in the esters 

( doubly bound oxygen O"— 

in the aldehydes and ketones 
in the acids 

in combination with P, S, and N 
ring oxygen 

(as in ethereal compounds). 


Alkyl. 

Aromatic. 

6-4 

r 6 

7*4 

9*1 

7-6 

9 * 5 -ii*o 

7*4 

IO-II 

7*4 


12*0 



8*3- 9*2 
7-4-11*0 


Sulphur S. 

There are two values for this element 

(a) S 25*6 (b) 21*6-22*5. 

The first is found in the mercaptans and the thio-ethers, also 
in those which show differences among themselves in the valency 
values of sulphur: —S— as in Cl—S—Cl, in the mercaptans 
R—S—H and thio-ethers R—S—R', also in a few inorganic 

1 

compounds with =S= and =S=. 

1 

( 6 ) The second value is found in the following groups: 
—S—C=N; —N=C=S, also in S=C=S, and ring sulphur. 
No other value for =S is found. 


Nitrogen N. 

There are two characteristic types of nitrogen :— 

(a) 15*6 for N=N, and in a few simpler compounds like 
NH S , NClg, N a O, N 2 0 4 , and in the groups 

—S—C=N, —N : C>, — S-C=N, —N=C=S, 
also possibly in others. 


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SUMMARY OF THEORY OF MOLECULAR VOLUMES . 239 

( b ) Amino nitrogen 

in the primary amines with the group—NH a , 10*5 
in the secondary amines—NHR— and —NR a , 12*0 

It has been hitherto supposed that only polyvalent elements 
vary in volume, but we shall see that probably others also do so. 

Chlorine Cl. 

Terminal chlorine Cl' 21*6 
Medial chlorine Cl" 24*6 

R—Cl' R—CHC 1 "—R' 

A number of intermediate values are found. 

When attached to the nucleus of benzene two distinct values 
for chlorine are known, 19*0 and 21*6. 

B. Constitutive Influences. 

The physical property of molecular volumes is marked to a 
considerable extent by the influence of constitution. The chief 
influences which have been worked out in this volume will be 
briefly described here. 

(a) The Influence of the Homologous Increment 

An exact study of the mode of variation of the volumes of 
the atoms in a number of series may be made by utilizing the 
following principle:— 

The relative volumes of the atoms remain the same in the 
different members of a homologous series , although their actual 
volumes differ from one another . 

This has enabled us by means of the relation 

v m = ws 

where W is the number of hydrogen equivalents, to find S the 
volume of hydrogen or its equivalent. 

The series of values so found for any homologous series, may 
be represented by curves which show the variation of the atomic 
volumes throughout the series. 

By this means, we have been able to show that the volumes 
of the atoms of the first two or three compounds in each series, 
and, therefore, those of the compounds, are relatively large. The 
values decrease to a minimum at about the fifth member in each 
series and then increase in the remaining compounds. 

These curves cannot be exactly represented by any formula, 


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240 


LIQUID CHEMICAL COMPOUNDS. 


but utilizing the fact that the mode of variation after the fifth 
member is nearly rectilinear, we may utilize the following formula 
to calculate the volumes of the compounds in a series :— 

v#n = w {S + (W - N)K} 

W being the number of hydrogen equivalents of a compound. 

S the volume of hydrogen which is least in a series. 

N the number of hydrogen equivalents in the corresponding 
compound. 

K the increment in the volume of hydrogen or its equivalent 
when hydrogen or its equivalent is added to a compound. 

For particular series the formulae are :— 

For the normal paraffin series C w H 2n+2 , 

Vm = (6 n + 2) {3*681 + (6 n - 36) x 0*0045}. 

For the formic ester series H . COOR, 

Vm = (6 n + 7) {3*647 + (6 n - 28) x 0*00375}. 

For the alkyl iodide series C*H 2M+1 I, 

v m = (6 n + 11) {3-671 + (6« - 24) x 0*00433}. 

n is the number of carbon atoms in a compound. 

C = 4 H, O' = 2H, O" = 3H, Cl = 6H, Br = 7*6H, I = 10H. 

The method may be useful to calculate the volume of a com¬ 
pound high in any particular series. 

Thus, if we require to find the molecular volume of say 
heptyl iodide C w H 2n+1 I, we find by use of formula 3 shown above 
the following result. 

Vm (calc.) 198*7 Vm (obs.) 198*6 

The method may be useful in cases which have not been 
investigated experimentally— 

as e.g. n decane 

Vm (calc.) 234*8 V m (by form.) 234*9 
using formula 1 above. 

In the aromatic series of the phenolic, cresylic, and other 
ethers, the benzoates and other series, it is found that the 
addition of the homologous increment CH 2 beyond the third, 
attached to the nucleus involves a total increase in volume of 37 
per CH 2 increase. 


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SUMMARY OF THEORY OF MOLECULAR VOLUMES. 241 


p Cresylic heptyl oxide. 
C 6 H 4 (CH 8 )OC 7 H 15 


v w 298*3 


c (&; 

89*6 

25*5 

0 

5*6 

c 7 h 15 

159*1 


279-8 

(Cs-C 8 ) 

i8-S (5 x 37 ) 

2nVa 

298-3 


298-3 


Unfortunately very few series have been examined with that 
degree of accuracy which would make the method generally 
useful, but sufficient evidence has been given to show us that we 
can extend the scope of our inquiries to fairly complex com¬ 
pounds, if we possess the requisite material for calculation. 

(b) The Influence of Unsaturation . 

(i) It is a remarkable fact that, for the most part, unsaturation 
produces no apparent effect on the molecular volumes of com¬ 
pounds, other than that which is occasioned by the subtraction 
of atoms. It is true that saturated and unsaturated compounds 
differ in volume by about that amount which is due to their 
difference in composition. This difference in composition, as a 
rule, is two or four atoms of hydrogen. 


Unsaturated Compounds. 


Compounds. 

Vm. 

A Vw, 

b.p. 

C.H 1S 

117*8 

7.7 

38*0 

C b H 10 |=| 

c»h 8 |=u 

110*1 

103*9 

2 x 7*0 (app.) 

39 *o 

C.H, . CH 2 . CH, 

139*3 

7*9 

136*5 

C e H„ . CH : CH, 

131*4 

2 x 6-55 

146*2 

C„H S . C ; CH 

126*2 


141*6 

C s H,OH 

81*4 

7*3 

97*1 

CjHjOH 

74*1 


94*4 

C s H 7 C 1 

91*9 

6*9 

46*0 

c 8 h 8 ci 

85*0 


46*0 

N(C 8 H,) 8 

222*5 

3 x 7*2 

— 

N(C 8 H 6 ) 8 

2007 

16 


— 


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LIQUID CHEMICAL COMPOUNDS. 


The average volume of hydrogen in both saturated and un¬ 
saturated compounds is about 37 and H 2 = 7*4. This is seen 
from the foregoing table:— 

Comparatively few unsaturated compounds are available for 
study, but there seems to be some disturbance, when an un- 
saturated atom or group is in association with a | = | or |=| 
link. 

We have just studied the group 

—CH 2 =CH 2 — 

(ii) When, however, the group is 

—ch 3 =chx— 

where X is such unsaturated atom or group there is generally an 
increase in volume. For example, 


Ethylene bromide CH 2 Br . CH a Br 
V m 977 

Acetylene dibromide CHBr : CHBr 
Vw 92*3 

A for H a 5*4 Now H 2 equals 7*3. 
The relative increase is therefore 

+ 1*9 

This can be otherwise calculated 


C 2 H 4 Br 2 


c 2 h 4 

43'2 (2 X 21’6) 

c 2 h 2 

2Br 

54'4 (2 x 27*2) 

2Br 

2nVa 

976 

2»V a 

V m 

977 

Vm 


36*0 

54*4 

90*4 

92*3 

+ i*9 


Acetylene tetrachloride. 
CHClj . CHClj 

b.p. 147*0 do 1*614 C 0*45 
Vm 120*5 

or CC 1 8 . CHC 1 2 138*2 (Thorpe) 

less Cl - 21*6 

plus H 
5nV a 

V m 


Ii6*6 

+ 37 

120*3 

120*5 


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SUMMARY OF THEORY OF MOLECULAR VOLUMES . 243 


Tetrachl or ethylene. 

CCl, : CCI, 

V w 114*8 

A for H a 57 H a 7*3 

Increase + 1*3 

The augmentation is not due to the chlorine atoms directly, 
since it is not affected by their number. We must consequently 
ascribe it to the ethenoid linkage | = | 

Tribrom methane. Tribrom methylene. 

CH 2 Br . CHBr a A CHBr : CBr a 

Vm 119*3 57 Vm 113*6 

The above cases involve a halogen atom on both sides of the 
ethenoid link | = |, and in such circumstances the apparent in¬ 
fluence of these halogen atoms thereon seems indubitable. 

Cases occur in which a halogen atom only is found, and the 
evidence is here somewhat contradictory. 

Ethylidene chloride. Unsymm. dichlorethylene. 

CH, . CHCL, CH a = CC4 

Vm 88*9 (by obs.) Vm 79*9 (by obs.) 

C = 0*46 89 o (by form.) 8o*i (by form.) 

* A 8-g 

7*2 for H a and A - 1*7. 

In this case the volume of CH 2 = CC 1 2 is diminished instead of 
increased by the amount 1 7, but there is apparently some dis¬ 
turbing influence. 

It will have been noticed that in the compound CC 1 2 : CC 1 2 , 
the value of A is + 1*3, which thus shows a relative expansion 
as compared with the saturated compound. 

In the case of the bromine compound, the result is different— 


CH, . CHBr a 


CH a : CBr a 

99*8 

6-8 

A + i *4 

93 *o 

CH, . CH a Br 


CH a : CHBr 

77 * 1 

5*8 

A + 1*4 

7 i *3 


In calculating the values for derivatives of ethane, it is neces¬ 
sary to use considerably larger atomic values, than for propyl 
derivatives. This complicates matters. The reason is, that as 
we pass from methyl (CH 3 ), ethyl (C 2 H 6 ), and propyl (C 3 H 7 ) 
derivatives, the change in volume for the addition of CH 2 is 
usually considerable. It follows that the volume of hydrogen 
will largely depend upon what atom or group is the substituent 
of ethane. The volume of hydrogen for the bromine compounds 
under consideration is about 3*8. 

16* 


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244 LIQUID CHEMICAL COMPOUNDS. 

(iii) It is probable that there is also some volume disturbance 
in the groups 

—CH(CH 8 ) : CHj— , —CH(CHj): CH(CH S )— 

due to the presence of the methyl group. 

The effect of other groups, if any, is not known at present. 

(iv) It has been shown that in the aromatic halogen com¬ 
pounds the volumes are similar to those in paraffinoid derivatives. 

C e H 5 Cl V w 114*6 Cl 21*8 Cl (paraff.) 21*6 

C e H fi Br Vnt 120*0 Br 27*2 Br „ 27*0 

C 6 H 5 I V m 130*7 I 37*9 I „ 37*0 

Most of the other unsaturated atoms and groups show a 
diminution when attached to the radical C 6 H 6 . Halogen com¬ 
pounds apparently do not. If however we suppose that in the 
group 

^C—Cl 

JL 

the usual diminution of - 15, due to the combination of 
chlorine with the C 6 H 6 group, be neutralized by the augmenta¬ 
tion + I'S, caused by association of chlorine with the | = |, we 
have a possible explanation of the exceptions to the rule just 
noticed. 

We notice that the apparent volume of iodine is considerably 
larger in C„H 5 I (as in allyl and propargyl iodides) than in 
saturated derivatives. 

The effect of the increasing magnitude of the substituent is 
seen in the compounds just mentioned. 


Propyl compounds. 

Vm. 

A. 

V m . 

Allyl compounds. 

CH g . CH a . CH a Cl 

91*4 

7*2 

84*2 

CH a : CH . CH 2 C 1 

CH 8 . CH a . CH a Br 

97*4 

6*9 

90*5 

CH a : CH . CH a Br 

CH 8 . CH a . CH a I 

106*9 

57 

101*2 

CH a : CH . CH a I 

CH 8 . CH a . COOCH 8 

104*2 

5*8 

984 

CH a : CH . COOCHj 

CH 8 . CH a . CH a Cl 

92*0 


777 

Propargyl compounds. 
CH : C . CHjCl 

CHj . CH a . CH a I 

107*1 

12*5 

94*6 

CH : C . CH a I 


A thorough investigation of all these phenomena would 
enable us to solve many problems of constitution, such as, for 
instance, differentiation between compounds of the types 

CH S . CH : CH a X and CH a : CH . CH a X 


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SUMMARY OF THEORY OF MOLECULAR VOLUMES . 245 
(c) Partial Ring Structure . 

Intermediate between open and closed chain compounds are 
what are known as 


Partial or Incomplete Rings. 

In order that they may be formed, it is necessary that two 
atoms or groups, which may be supposed to possess residual 
affinity, occur in a hydrocarbon chain attached to different carbon 
atoms. If the carbons are near to each other, there is no need to 
suppose any variation from structure usually considered when 
the tetrahedral arrangement of the valency links of carbon is 
understood. The additional feature of curvature of the hydro¬ 
carbon chain may also be the normal condition of things. In 
the case of saturated compounds the plane formulae are figured 
thus — 


CH 2 

CHj 



1 


J 


CH 2 -X N 

I ) 

CH- Y / 

ch 3 


If the two attracting groups are united to carbons not in the 
immediate neighbourhood of each other, we must suppose that 
they are brought near by the curvature of the hydrocarbon chain, 
or the alternative supposition just given is true. In any case such 
a structure affects the molecular volumes of compounds. 

Thus— 


CH^ 


-X\ 


CH„- 


) 


CH. 


-T 


CH- 


~X\ 

\ 

I 

J 


If the compound be unsaturated, it is necessary to suppose 
two forms which may thus be represented— 


CH- 


X-CH 

II 

CH- 

_ Y / 

II 

CH-Y 

The syn compound. 

The anti-compound. 


The former would be smaller in volume. 


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246 


LIQUID CHEMICAL COMPOUNDS . 


We must also suppose that in the benzene di-substituted 
molecule the ortho form would be 


\ 



This, however, according to the tetrahedral arrangement of the 
carbon links, could be given two types of arrangement: one in 
which the atoms or groups appeared on the same side of the 
ring and one in which they would be disposed on the opposite 
sides. 

It should be remarked that in the saturated chain there is no 
hindrance to the two reactive groups occupying the sign position, 
so that only one form is possible. In the unsaturated chain the 
possible rotation about an axis joining two carbon atoms is pre¬ 
vented by the residual affinity associated with an ethenoid link. 
Two forms are thus possible. 

The attracting atoms or groups are the halogen atoms 
Cl, Br, I, the hydroxyl group OH, the amino NH 2 , etc., the 
nitro N 0 2 , the carboxyl COOH, and perhaps other groups. 

The contraction 

for a /9 compounds is about - 3*0 
1 > ay »» >f “4*5 

In ring-compounds the ortho arrangement has been specially 
studied (q.v.). 


(d) Ring Structure. 

This subject has already been dealt with at some length, but 
the chief points can here be stated. 

Ring compounds are invariably characterized by contractions. 
This is due to a diminution in the individual atomic volumes 
forming the nucleus, and also in the case of the associated 
hydrogen atoms, when such are present. 

The compounds ( a ) benzene and (b) hexamethylene have been 
studied not only at the critical and boiling-points but also at 
corresponding pressures, and it has been shown that the relative 
volumes of the atoms remain the same as in straight-chain 
compounds . 


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SUMMARY OF THEORY OF MOLECULAR VOLUMES. 247 

The contractions for single-ringed compounds are 
□a - 6*5 D4 - 8 *5 Ds - IX *5 □« - !5’o □? - 20-0 Os - 25*5 

Double and triple rings have contractions 

I I I 6+ 5 “ 26*0 I | l a x 6 - 30*0 camphor, etc. - 31*0 
1 I 1 la x 6 - 4 8 *° IM 1 * x s + b “ 45 *° 

Not many independent double-ring compounds are available for 
study. 


(e) Molecular Volume and Valency . 

It has been supposed that there is a connection between 
volume and valency. However this may be in a general sense> 
there is no clear connection between the volume and the funda¬ 
mental valency. When, however, we compare the atomic 
volumes in the different series of the periodic arrangement of the 
elements, we find a general indication of a similar increase from 
series to series. For example:— 


Averages. 


Series I 

C 14*8 

N 15-6 

0 ii’o 

F 87 


A 

+ 17*2 

+ 14*6 

+ n *4 

+ 13*4 

I 4 *I = 4X37 

Series II 

Si 32*0 

P 27*0 

S 22-0 \ 
25*6 J 

Cl 22*0 





M. 23*8 



A 

+ 37 

+ 5*o 

+ 3*6 

+ 4*9 

4*3 = i x 4*3 

Series III 

Ti 357 

V 32*0 

Cr 27-4 

Br 27*0 



Ge 35-1 

As 27*0 


Br 27*0 


A 

+ 6-g 

+ 7*3 


+ 10*0 

8 # o = 2 x 4*0 


Sn 42*0 

34*3 

— 

I 37-0 



These differences vary somewhat, but they are similar. It is, 
however, probable that the numbers themselves, which vary con¬ 
siderably under different circumstances and with various environ¬ 
ments, are not quite the significant volumes. In order to arrive 
at a generalization of more than qualitative significance, it is 
necessary to know precisely what the term molecular volume 
stands for and it is also necessary that the atoms should be 
placed under comparable conditions. How much of the real 
molecular volume space consists of atoms with their shells, and 
how much is made up of their movements of vibration we do not 
know. It is possible that some simple relation between volume 
and valency, similar to that discovered by Barlow and Pope, might 
be discovered if we could divide up the apparent volumes into 
their real parts. This may one day be possible, and the relation, 
one of simple proportionality, discovered. 


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248 


LIQUID CHEMICAL COMPOUNDS . 


The unit 37 seems to be significant for (a) several atoms are 
integral multiples of this unit— 

C 14-8 = 4S h = 37 = s o = n*o = 3S s = 25-6 = 7S. 

Also (b) several atoms of varying atomic volume seem to 
show volumes which differ by just this unit— 


7*4 

S 22*0 

N 12*0 

11*0 

25*6 

15*6 

3*6 

3*6 

~6 


The possibility of variation in the atomic volumes cor¬ 
responding to variations in acting valency thus occurs. 

It has been thought that as the acting valency of an atom 
changes its volume varies also. This is found not to be the case. 

Thorpe has stated this in the course of his work on molecular 
volumes. Thus: “The inquiry affords us no evidence in favour 
of the hypothesis that the specific volume of an element in com¬ 
bination is modified by any possible variation in the affinity value 
which it may possess. The observation of compounds of sulphur 
and phosphorus appear conclusive on this point.” 

We do not know how Thorpe came to this conclusion, since 
his formulae make phosphorus trivalent and sulphur divalent— 

C \ 

P—0C1 Cl—S—0C1 CIO—S—0C1 

• Cl^ 

With the accepted formulae, which are confirmed by means of 
our theory, we find that phosphorus and sulphur may act with 
varying valencies. There is, however, no change in the atomic 
volumes of the elements due to this cause, as Thorpe supposed. 

Cl 

/ 

Cl—P 

\ 

Cl 

or P*“ 27*0 

It should be mentioned that Prideaux* values for PC 1 5 and 
PBr 6 seem to lead to a different conclusion, but his observations 
are capable of another explanation (q.v.), and in any case are 
exceptional. 


Cl 

/ 

0=P—Br 
\ 

Cl 

P v 27*0 


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SUMMARY OF THEORY OF MOLECULAR VOLUMES . 249 


Cl—S—Cl 

S" 25*6 


Q=N—Cl 


N'" 15*6 


Cl 

/ 

o—s 

\ 

Cl 

Siv 25*6 


C.H^O—N 


O Cl 

\ / 

s 

^ \ 

O Cl 

Svi 25*6 

o 


\ 


Nv 15*6 


We do not possess the requisite data for any other elements, but 
the results just obtained appear conclusive on this matter. 

It is true that the volumes of the elements vary, but this 
variation cannot be shown to be due to their variable valency 
relations, but to some other cause. 

S" 21*5 and 25*6 

N"' 12 15*6 

O" 7*4 n*o 

Br 27*0 to 28*5 


(/) The Constitutive Influences Due to Groups. 

The question of special influences due to groups is a very 
important one, and for thorough treatment many more accurate 
data are needed than are at present available. In so far as the 
homologous open-chain series are concerned, the additive rule 
may, for practical purposes, be said to prevail, unless the com¬ 
plexity be greater than a certain amount. 


Volumes of Groups in Organic Compounds . 

CH S 26*0 C 2 H a 48*0 C 3 H 7 70*0 C 4 H 9 92*3 C 6 H a 92*8 

OH io*o CHO 25‘9 CO 22*0 COOH 37*8 

NH 2 17*4 N 0 2 32*0 CN 30*4 S. CN 52*0 

The volumes are average ones for the groups in question, but 
they do not vary very much under ordinary circumstances except 
perhaps for the group CH 3 . Taking the average volumes of the 
atoms already indicated, we find how the volumes of the groups 
CH 3 and C 2 H 5 may vary according to the particular typical atom 
or group to which it is attached. The ethyl CH 3 group varies 
most, the C 2 H 5 group to a lesser extent, and both vary most 


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250 


LIQUID CHEMICAL COMPOUNDS . 


when H,OH and Cl are the other groups making up the com¬ 
pound. These variations are due to causes not quite understood 
as yet, but probably complexity is one of them. 

It is also possible that there may be some interactions be¬ 
tween the alkyl and other groups. An important example of 
variation in the values of the groups is found when they are 
attached to aromatic radicals like phenyl C 6 H 5 . The volume 
of this group is taken as 92*8, and the volumes of the other 
groups as in the preceding table. 


The Contractions Found when Unsaturated Groups are in 
Union with the Phenyl Group C 6 H 5 . 


Group. 

A. 

Group. 

A. 

Group. A. 

—OH 

-0*9 

—COOH 

- 3*9 

CH S and \ 

—CN 

-1-6 

—CH 2 C 1 

-i *9 

other alkyl > - 0*5 

-nh 2 

“ 4*3 

—no 2 

-27 

groups * 

—COC 1 

-i-8 

—PC 1 2 

- 2*0 


These variations may be ascribed to some interaction between 
the phenyl C 6 H 5 radical and the unsaturated groups. For this 
reason the formulae, representing this constitutive action, may be 
shown generally as— 


^ CH \ 

H C—-X 


CH CH 

ch/ 


X representing the unsaturated group. 

It is easy to show that unsaturation is the cause, because 
when the hydrogen in the OH and COOH groups are replaced 
by alkyl groups like CH 3 the contractions disappear. 


Phenol 

Anisol 

C,H 5 . OH 

C,H S . OCH, 

Vm 

102*0 

125*4 

2 «Va 

102*9 

125*2 

A 

-0*9 

Benzyl alcohol 

Anisol 

C 4 H„ . CH,OH 

CjH e . OCH, 

1237 

125*4 

125*2 

125*2 

-i *5 

Benzoic acid 

Ethyl benzoate 

C 6 H 6 . COOH 

C,H, . COOC,H, 

126*9 

x 74*4 

130*6 

174*1 

- 3*7 

Phenyl propionic acid 
Ethyl benzoate 

C„H,. CH, . CH,COOH 
CjH,. COOC,H, 

170*9 

174*4 

174*1 

174*1 

- 3*2 


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SUMMARY OF THEORY OF MOLECULAR VOLUMES . 251 


It has already been shown that the group NH 2 is responsible 
for a contraction of - 4*3. It is remarkable that the groups 
—N(CH 3 ) 2 , —N(C 2 H 5 ) 2 produce the same contraction, a fact 
which points to the common atom nitrogen as being the part 
affected. If the group be unsaturated, e.g. N(C 8 H 5 ) 2 , the contrac¬ 
tion is apparently greater. 

Not many other groups have been sufficiently studied, but 
cases which are subject to such contractions may be given. For 
instance, if we compare 

R—OH and R—O—R 
R—NH a and R-NH-R or R^=N—R 

we find that 

O = 6*4 and io*o 
N = 10*5 and 12*0 

Such cases are, however, difficult to adequately account for. This 
is one of the great difficulties which attend the study of the mole¬ 
cular volumes of open-chain organic compounds, for it is not 
quite clear whether and to what extent the individual groups 
making up these compounds influence one another. Such a 
study is easy in ring compounds such as benzene derivatives, and 
under such circumstances a fairly complete and reliable analysis 
has been made. 


C. A discussion of the special conception embodied in mol¬ 
ecular volumes, and the relation which obtains between 
this property and other physical properties such as boil¬ 
ing point, surface tension and viscosity. 

A discussion of the special conception embodied in molecular 
volumes, and the relation which obtains between this property 
and other physical properties such as boiling point, surface ten¬ 
sion and viscosity. 

It is hardly possible in a formal treatise like the present to 
altogether avoid dealing to some extent with the physical mean¬ 
ing of molecular volumes, and the derived conception of atomic 
volume. 


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LIQUID CHEMICAL COMPOUNDS . 


If the specific volume = - in c.c., then the molecular volume of 
a 


say pentane C 5 H 12 is 


g- MW 72 

0'6l2 ——=—- = 117-6 

d o # 6i2 


at the normal boiling-point 

The molecular volume in the first instance is the volume of 
that weight which represents the weight of the molecule, or the 
molecular weight multiplied by the specific volume. This volume 
under well-defined conditions such as those obtaining at the boil¬ 
ing-point may be supposed to bear to the real molecular volumes, 
a relation, which is the same for all substances, and thus pro¬ 
portional to the real molecular volumes. Jhis was assumed by 
Kopp when he started on his investigations of the molecular 
volumes of liquid organic compounds at the boiling-point, and 
this has been justified by subsequent work. 

It has been shown that 


Vb.p. = 3 / 8 V. 
but Vo = V 4 Vc 
... v b .p. = * x a Vo = s / 2 Vo 

that is, the volumes of the most various liquid compounds are, 
at the normal boiling-point, one and a halftimes the volume at 
absolute zero. This volume V 0 is consequently proportional to 
the real molecular volume, and so are also the volumes at the 
boiling-point V b . p .. 

If the law were strictly followed, the investigation of the 
molecular volumes of compounds would be a simpler matter 
than it is. It depends upon the fact that the internal pressures 
are the same for all compounds at the boiling-point, subject to 
small variations due to differences in complexity and other 
causes. These disturbances destroy the simplicity of the rules 
regulating the relation between the atomic volumes to the whole 
molecular volume. Young, who investigated a number of organic 
substances minutely, from the point of view of Van der Waal’s 
equation of condition, attributes the departures from Van der 
Waal’s theory to the constitutive influences. 

We have reason to believe that in liquids the molecules exist 
under an intense intermolecular pressure, which affects the boil¬ 
ing-points of the compounds, their surface tensions, and their 
viscosities. These intermolecular affinity forces act in such a way 
as to oppose the heat forces, which consist of vibratory movements 


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SUMMARY OF THEORY OF MOLECULAR VOLUMES . 253 


of some kind. The intermolecular forces, presumably of great 
magnitude, together with the heat forces serve to limit the 
molecular motions and define the space called the molecular 
volume. If we consider simply those portions of the molecules 
called the nuclei, measured by 3V D , in the Lorenz-Lorentz formula, 
or considered in the Clausius theory, it is impossible that they 
should completely fill the space occupied known as the molecular 
volume. There must of necessity be a molecular interspace as 
well as possibly atomic interspaces. This interspace is measured 
by V - b according to Van der Waal’s formula. 

We may now consider the question :— 

(a) Of what constitutes the atom and consequently the 
molecule, and 

(< b ) What is the nature of the molecular movement ? 

If the Boscovitchian hard atom cannot be entertained, owing 
to the necessity of accounting for the elastic properties of matter, 
we must suppose that the nucleus just referred to is enclosed 
within a shell of dielectric. We consider in the first place that 
the molecule is made up of the atomic nuclei and its real volume 
is equal to their sum. The atomic nucleus is however not the 
whole of the atom, for if we were to cool a substance to absolute 
zero we should find that it occupied a volume considerably in 
excess of that of this molecular skeleton so to speak. In other 
words the term b of Van der Waal’s formula is considerably 
larger than 37 b of the Clausius theory. Traube supposes that, 

b = 3-5 or 4 2V D . 

He iemploys the molecular refraction as a measure of the 
nuclear volumes of the atoms contained in a substance, and 
moreover calculates that the molecular refraction of a saturated 
compound is proportional to the number of valencies of the com¬ 
ponent atoms. At any rate this atomic shell represents that 
portion of the atom which is permeable to light, and constitutes 
that dielectric medium which enables electro-magnetic radiations 
generally to traverse the liquid at a speed which is characteristic 
of the particular liquid under consideration. The molecular volume 
at absolute zero is thus equal to the sum of the atomic nuclei plus 
the sum of the dielectric shells . It may be supposed that the 
chemical forces which bind atom to atom to form a molecular 
combination, is accompanied by stresses and strains in this 
dielectric. 


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LIQUID CHEMICAL COMPOUNDS. 


We are now asked to consider a space equal to one and a half 
times the volumes of all the atomic nuclei in the molecule:— 
since Vb.p. = $ Vo = $ b. 

That this space is occasioned by motion of some kind, is obvious, 
but on the nature of this motion there has been much dispute. 
One consideration, which may prove of considerable importance, 
has never been commented on to the best of our knowledge. 

It is this,—why may not the dielectric medium itself expand 
with rising temperature and fill up the extra space occupied by 
the liquid caused by the separation of the molecular and also the 
atomic centres ? It is not difficult to imagine such a condition. 
We may suppose for instance that the dielectric consists of a 
series of shells of diminishing magnitude as we approach the 
centre, and related in such a way that a central section would 
show a spiral originating from the atomic nucleus. Energy could 
become latent by the “ solid spiral ” contracting as a watch spring 
contracts when it is wound up, and moreover could vibrate by a 
repeated winding and unwinding within limits dependent on the 
stress within the medium as an ordinary spring might do. Such 
a motion of the shell, combined with the resultant motion of the 
nucleus, would constitute the heat motion. We do not insist on 
this particular mechanism, but give it for what it is worth. The 
idea of a dielectric expands as the temperature rises, is, however, 
worthy of every consideration, for we know that the index of 
refraction fi , and therefore the velocity of light in the particular 
liquid medium, is a function of the temperature. It may be stated 
that the dielectric shells might not be susceptible to differences 
in density from compound to compound or for one compound 
under various conditions, in the same sense that matter in general 
differs in density. The differences might consist of different 
degrees or kinds of strain. 

If we consider the whole molecule and its expansion under the 
influence of temperature, we see that there is every reason to sup¬ 
pose that under circumstances of equal internal pressure or under 
corresponding conditions, the volumes of the molecules should be 
proportional to their absolute zero volumes and thus of their real 
molecular volumes. It is however possible, and indeed probable, 
that as we approach the critical point, certain disturbances might 
occur which cause departures*from ideal conditions, and from the 
more simple conditions which occur at or near absolute zero. 


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SUMMARY OF THEORY OF MOLECULAR VOLUMES . 255 


This, in effect, is the result of the remarkably short range of the 
affinity forces, and the consequent rapid variation with the distance 
between the molecular centres. It follows that constitutive 
features which are apparent at or near the melting point are to 
some extent marked at and above the boiling point. 

The Visibility of the Liquid. 

In our view, one circumstance of great significance is, that, 
when a vapour condenses it becomes visible. Steam, for example, 
condenses to a transparent but visible liquid water, which, except 
for conditions of mobility, maintains certain characteristics be¬ 
low the melting-point and in the solid state which are noticed 
in the liquid. The clear limpid water solidifies to the clear 
glassy ice and this characteristic is maintained down to absolute 
zero. For that matter an opaque liquid like mercury maintains 
this characteristic below the melting-point, and so far as we know 
even to absolute zero. In both cases, however, the vapours are 
transparent. The reason is, that in the vapours, the light passes 
through the interspaces which separate the molecules, but in liquids 
when transparent, it passes through a different medium, the dielec¬ 
tric shells of the atoms and possibly of the molecules as a whole, 
and this condition is maintained down to absolute zero. We 
believe that the features just noted can only be explained on the 
assumption of compact structure in the sense indicated. It is also 
to be remarked that the theory of absorption spectra implies that 
light traverses a medium different to that of the external ether. 

It is not difficult to understand why Richards should have 
come to the conclusion that the atoms in a liquid as in a solid 
molecule are in actual contact with each other. We think that, 
it is necessary to go a step farther and to suppose that the mole¬ 
cules as just defined, are also in actual contact. It is thus 
found that liquids are compact aggregations of molecules of de¬ 
finite and characteristic compressibility under well-defined condi¬ 
tions, and that the compressibility of the liquid as a whole, measures 
the compressibility of the dielectric associated with the atomic 
nuclei. The question of the mobility of the molecules under such 
circumstances will be referred to immediately. 

Another idea of considerable moment, and one derived from 
a study of molecular volumes, is that if there is considerable 
motion of translation of the molecules with its consequent impacts, 
then these motions of translation will depend upon the molecular 


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256 


LIQUID CHEMICAL COMPOUNDS. 


weights. We should thus expect that a heavy molecule like 
Ci 6 H 84 , would slow down as compared with a light one like 
butane (C 4 H 10 ) or pentane (C 5 H 12 ). 

According to the kinetic theory 

pressure p = MNV 2 

M representing molecular weight, N the number of molecules, V 
the velocity. 

If we compare two molecules of different complexities then 
for 1 gr. mol. of each substance 

P\ _ Mi Yh 

/ a “M a vv 

Since at the boiling-point p x = p 2 

Mi_YV r 

M a ~ V\ or 

(velocity)* 00 moIecul ^ weight - 

Thus a small molecule like C 6 H 10 might be expected to 
occupy a large volume as compared with a heavy one like 

QoH 84 . 

We find that the opposite is the case. Pentane C 5 H 12 at the 
boiling-point occupies a volume of 117*8. A similar complex in 
octane C 8 H 18 occupies a volume of 

32 x 3 725 
= 119*2 

The difference would be much greater if hexadecane C 16 H 34 
were under consideration. 

The Motion of a Molecule through the Liquid Mass . 

It is not difficult to imagine that, under such conditions, an 
aggregation of elastic substances, endowed with enormous amounts 
of kinetic energy, might diffuse or migrate excessively slowly 
against the intense fields of force which are consequent on the inter- 
molecular residual affinities. We cannot conceive of the existence 
of the excessively slow motion characteristic of the molecules, even 
in dilute solutions, on any other assumption than the one already 
made. The motion of a molecule in a liquid mass may be compared 
to that of the motion of a comparatively large mass (like a projected 
bullet) through a viscous medium like tar.or treacle, as compared 
with its ordinary motion through the air. The analogy is still 


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SUMMARY OR THEORY OR MOLECULAR VOLUMES. 257 


incomplete since the bullet has no affinity for the medium through 
which it is passing. 

It may be remarked in conclusion that a consideration of the 
molecular volumes from the present point of view is really inde¬ 
pendent of these theoretical questions, and depends only on the 
empirical rule that the volumes at the boiling-point are for the 
most various substances four times the volumes at absolute zero. 

It now remains for us to consider how it is that the molecular 
volumes reflect so accurately the chemical constitutions of sub¬ 
stances. In dealing with molecular volumes, it is necessary to 
take into account such properties as boiling-point, viscosity, and 
surface tension. We should however note that boiling-points do 
not always indicate differences in chemical constitution, nor show 
results which are evident from a study of molecular volumes. For 
instance variation in molecular volume and boiling-point are not 
affected to the same degree, by such constitutive features as ring 
structure. 


Dipropargyl C 6 H 8 . 

CH : C . CH 2 . CH 2 . C : CH 
Volume m*o A - 15*0 

Boiling-point 85*0 A - 47 


Benzene. 

c 6 h 6 

96*0 

80*3 


The variations of the boiling-points for a given chemical 
change are usually greatly in excess of the volume changes, but 
not in this case. On the other hand, differences in boiling-point 
are often accompanied by well-defined changes in volume, but 
the latter are most frequently in the opposite direction—that is, 
when the one is positive the other is negative. The intermole- 
cular forces are doubtless of considerable importance in deter¬ 
mining the molecular volume, and these may be considered to be 
determined by the forces of residual affinity arising from the in¬ 
dividual atoms. It has been shown that the range of the mole¬ 
cular activity or influence is equal to the distance which separates 
two molecular centres. The molecular forces influence such 
physical properties as 

(a) The boiling-point .—For example, that compound which 
possesses the highest boiling-point is obviously the most difficult 
to separate from its neighbours, and to endow with the kinetic 
energy necessary to cause vaporization. As already stated the 
effect upon the molecular volume is generally in the opposite 
direction to that upon the boiling-point. This is seen in such 
cases as 

17 


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253 LIQUID CHEMICAL COMPOUNDS. 


CH, . CH a . CH a Cl 
b.p. 46-5° 

A - io° 

(CHj) a CHC1 
36*5° 

Vm 92*0 

A + 2*3 

94*3 

CHj. CHBr a 
b.p. in-o 

A + 19*3 

CH a Br . CH a Br 
130*3 

V M 99*o 

A “ 2*0 

97*o 

CH S 

p c,h 4 <^ 

CHj 

b.p. 138*0 

A + 3*9 

CH, 

m C,H 4 <^ 

CH, 

141-9 

V w 140*2 

A - 2*3 

l 37'9 


The explanation which seems to best suit these cases is that the 
intermolecular forces are most intense in the higher boiling-point 
liquids (when two or more isomers are compared), and it is evident 
that the peculiarity which occasions this difference, is one which 
favours a more striking manifestation of intramolecular force 
than in the other case. It is natural then to suppose that the 
particular combination or spatial association of atoms or groups, 
or their distribution throughout the molecule, are the factors 
which cause the differences in the various cases. It should, 
however, be clearly understood that changes in the boiling-point 
are not always evidence of corresponding changes in the (a) mole¬ 
cular volumes , (b) surface tension , and (c) viscosity. 

It is natural to suppose that boiling-point, surface tension, 
and viscosity are parallel phenomena, for those influences which 
tend to increase or diminish one property, also influence the 
others. Thus we find :— 



b.p. 


Viscosity 

Surface tension. 




Vf X IO 6 . 

N x 1000 

n-hexane 

68*6 


221 




-6*6 

-13 


iso-hexane 

62*0 


208 


xylene 0 

141 


254 

16*0 



-2*0 

-21 

-0*1 

xylene m 

139 


233 

15*9 



- 1*0 

±0 

-0*1 

xylene p 



233 

15-8 


We see that any explanation of the peculiarities manifested 
by the molecular volumes of compounds must take into considera¬ 
tion the part intermolecular forces play in determining the mole¬ 
cular volumes of compounds as well as the intramolecular forces 
themselves. The latter may possibly in some cases be in the 
same direction as the intermolecular forces, or on the other hand be 
contrary to them. It probably is not easy to make these distinc- 


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SUMMARY OF THEORY OF MOLECULAR VOLUMES . 259 


tions in practice, nor clearly in every case to analyse the complex 
conditions which obtain. Some constitutive influences are evid¬ 
ent enough, such as those of ring structure, the contiguity of 
groups or separation of groups in dihalogen derivatives of the 
paraffins, and the ortho, meta, and para modifications of the di¬ 
substitution products of benzene, etc. The work which has been 
done in this volume, whilst to some extent useful for the ex¬ 
planations given of some of the phenomena, is probably of 
greatest value for the analysis of the effects themselves apart 
from their causes. The explanations will come later. Even 
as regards the effects, data are very meagre in many cases, and 
though the numbers obtained by means of the formula de¬ 
scribed in Appendix II. may be exceedingly useful as preliminary 
determinations of data, yet they can never carry the weight of the 
results of well-directed and well-executed experiments. It is to 
be hoped that the latter will soon largely increase. 

There is no doubt that in spite of the care taken, many parts 
of the present theory may have to be altered later as data ac¬ 
cumulate, and as our knowledge of the physical property increases. 
The identification and explanation of constitutive effects is not 
always easy. Some particular atomic values—generally those 
found in the homologous series R—X are taken as standard, 
and by the method of summation the value 2 nV a is found. The 
difference V w — 2 riV a then measures the constitutive effect. 
Sometimes a mean atomic value is taken, and it then follows that 
no account is taken of the variations. The great difficulty is to 
identify the effect with a particular atom or group. When this 
seems possible, it sometimes happens that other atoms or groups 
might equally well be identified with the effect in question. Only 
a careful examination of a large number of data can overcome 
these difficulties. It will generally be found that the constitutive 
effectsV w — S n V a are traceable to some modification in particular 
atomic values, and a considerable advance is made when we are 
able to ascertain for certain which atoms are marked by the 
variation in question, and by how much. 

For instance, the contraction for ring compounds like benzene 
C 6 H 6 amounts to -i5 # o. Careful inquiry shows that this is 
made up from a contraction of all the atoms in the nucleus 
C« 12*8 instead of 14*8 and H = 3*2. It follows that we know 
the volumes of such residues as C 6 H 5 —, C 6 H 4 = , etc., and so are 

17* 


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26 o 


LIQUID CHEMICAL COMPOUNDS. 


able to find out the volumes occupied by the side chains. For 
instance we show that the volume of CH 3 is the same in the 
homologues of benzene, if sufficiently separated. 



Vw. 

Benz. Rud. 

«CH a . 

CH a 

c.h b .ci 

Eij 118-25 

92-8 

— 

25*45 


«,), 140-51 

89-6 

50-91 

25*45 

1:3:5 C,H».jC 

Hj) 3 162-75 

86-4 

76-35 

25*45 


This knowledge may serve as a basis for the determination 
of the volumes of components of other aromatic compounds and 
also enable us to measure constitutive effects. 

OC 6 H 4 (CH 3 ) a Vw 137*6 C 6 H 4 89*6 

2CH3 50*9 

2»Va 140*5 
Vw 137*6 

A For ortho struct . - 2-9 

It happens in this case that SnV a is similar to the volume of 
p. xylene. In other cases this additional information may be 
lacking, and we depend on the regularity already observed. 
Greater simplicity is introduced into the work, for our guiding 
principle by being able to assume that in all these aromatic com¬ 
pounds the phenyl or similar radical, undergoes no change of 
volume in the different combinations. This enables us to deal 
with fairly complicated ring compounds. 

Much greater difficulty has been experienced with open-chain 
compounds, owing to our lack of ability to decide which atoms 
or groups take part in the constitutive effect. This is largely 
due to the fact that many constitutive effects are more or less 
affected by the general influence of complexity, which is not de¬ 
pendent on any simple law. 

It may also be stated that one reason why the effects may 
differ somewhat, in degree at any rate, under other conditions than 
those at the boiling-point, from the effects observed at this point, 
is just the effect of this temperature factor. We might expect 
that constitutive effects should be more prominent say at the 
melting-point than at the boiling-point, because in addition to 
the diminishing influence of the heat forces, the forces of affinity 
have increased according to some high power of the distance 
between the molecular centres, and may even change sign at 
some point It is also true that the effects may be different 
from those observed from the examination of other physical 


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SUMMARY OF THEORY OF MOLECULAR VOLUMES . 261 


properties such as refractive power, and magnetic rotatory power 
for just the reason that they do not possess a temperature factor 
as do molecular volumes. 

In consequence of the facts just mentioned, it is hoped that 
any deficiencies or irregularities found, will be leniently dealt 
with, and regarded as part of that unavoidable element of crudity 
which attaches to all theories in their initial stages. 


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APPENDIX I. 


A FORMULA BY MEANS OF WHICH THE MOLECULAR VOLUME AT 
THE BOILING-POINT MAY BE CALCULATED.* 

In an extended study of molecular volumes, it was found neces¬ 
sary to calculate some of the values at the boiling-point, and the follow¬ 
ing formula has been found suitable for this purpose:— 

t-‘~ ('-!£)■ 

The only data necessary are the density at o° and the boiling-point. 
The value of c is given in the following table, the data being those 
of Thorpe:— 


Table of Values (Inorganic Compounds ). 


Compound. 

B.p. 

do . 

dB.p. 

c . 

V*. 

calc. 

Vw. 

obs. 

Per cent 
error. 

saci 2 


• 139-6 

1*85846 

1*60610 

0*460 

135*5 

135*5 

+ 0*0 

SO,Cl. OH. 


• 155-3 

178474 

1*54874 

0*420 

75*5 

75*05 

+07 

SO,Cl a 

AsC 1 3 . 


. 70*0 

170814 

1*56025 

0*462 

86*3 

86*3 

+ 0*0 


. 130*2 

2*20500 

1*91813 

0*447 

95 *i 

94*37 

+ 0*76 

AsF 8 . 

VOCI3 . 


. 60*4 

2*6659 

2*4497 

0*490 

53*6 

53*84 

-0*44 


. 127*2 

1-86534 

1*63073 

0*452 

106*5 

106*2 

+0*3 

POBrCl a . 


• 137-6 

2*12065 

1*83844 

0*458 

107*5 

107*4 

+ 0*1 

PSClj. 


. 125-1 

1*66820 

1*45599 

0*455 

116*3 

ii6*i 

+0*2 

POCI3. 


. 107-2 

171163 

1*50967 

0*474 

101*0 

101*4 

-0*4 

JiCL . . 


• 136-4 

1*76041 

1*52223 

0*460 

124*5 

124*5 

+ 0*0 

SiCl 4 . 


• 57-6 

1*52408 

1*40294 

0*500 

120*2 

120*8 

-o *5 

N 2 0 4 . 


. 21*6 

1*49030 

1*43958 

0*473 

64*0 

63-9 

+ 0*0 


Mean value, 0*463. 


It is found that by means of the above formula the volumes of 
compounds of a similar order of complexity can be calculated to within 
1 per cent. 

273 d ° 

Example.—GeCl 4 , d w 1*887 (Winkler), b.p. 86*o°, = 0*760, y = 0*46 x 0*240 

1*887 

= 1*104, <*b.p. = = 1*709. M.W. = 213*8; V w . 125*1. 

Observed, C 14-8, Si 32, Ge [36*3], Sn 42*3, Ti [357]. 

The formula can be used indifferently for inorganic and organic 
compounds, but the value of c in the latter varies somewhat as the com¬ 
pounds vary greatly in complexity and the chains lengthen. 

* Adapted from “ Joum. Chem. Soc.” 

263 


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264 


LIQUID CHEMICAL COMPOUNDS, 


The value of c for organic cyclic compounds without side-chains is 
similar to the above. 


Cyclic Compounds . 


Compounds. 

M.p. 

oro°. 

B.p. 

du 

o° 

or m.p. 

d r 

T=B.p. 

c . 

Vm. 

calc. 

Vm. 

obs. 

Per cent 
error. 

C 8 H 6 (Benzene) 
C 4 H 4 S (Thiophen) . 
C 10 H 8 (N aphthalene) 
C 10 H 14 (Hexahydro- 
naphthalene) 
C 14 H 10 (Phenan¬ 

6-o° 

8o° 

0*8940 

0*8133 

0*470 

957 

96*0 

-0*03 

0*0 

84 

1*0884 

0-9874 

°*434 

85*5 

85*0 

+ o*6 

79-2 

217 

0*9777 

0*8674 

0*456 

147*3 

147*2 

+ 0*0 

0*0 

200 

0*9419 

07809 

0*487 

170*0 

171*2 

-07 

threne . 

100*5 

340 

1*0630 

0*9073 

0*440 

197*8 

195*2 

+ i # 3 

C 6 H 5 N (Pyridine) . 
C 9 H 7 N (Quinoline) . 

0*0 

0*0 

”5 

234 

1*0033 

1*1081 

0*8826 

0*9211 

0*462 

0*439 

89*3 

141*1 

« 9'3 

I40*0 

+ 0*0 
+o*8 



Mean value, 

0*460. 




The results of calculation show very fair agreement with observa¬ 
tion, and thus giving a fairly trustworthy method for the calculation of 
unknown values. 

Example.—Hydrindene , C 9 H 10 : d 5 0-957, b.p. 176°, £=46, V w . 
144-0. SnV a =*(4x9+ 10)3-7 = 46 x 37 = 170-2, A = - 26-2 
for ring. Contraction for 1 six-membered ring + 1 five-membered ring 
= - 15 “ n *5 = “ 26 5. 

Acenaphthene , C 12 H 8 .—The value of c for phenanthrene is 0*440. 
For acenaphthene, d lQZ 1*030, m.p. 103°, b.p. 277 0 . V m 166*6, 
2 «V a 207*2, A = - 40-6. Contraction for 2 six-membered rings + 1 
five-membered ring = - 30-0 - 11-5= -41*5. 

The only difficulty is met with in open-chain organic compounds. 

For compounds like chloroform, carbon tetrachloride, and trichloro- 
methane, the value of c mentioned above (0-460) may suffice. 

* c, in general, increases by 0*024 for every addition of CH 2 in open- 
chain compounds, thus:— 

C 6 H ia 0*476, C 6 H J4 0*500, C 7 H 16 0*532, C 8 H]£ 0*554, 

A 0*024 0*032 0*022 

When considering an unknown value for a certain compound, it is 
usually possible to find an analogous compound from which c may be 
calculated, for example, cymene, C 10 H 14 , for the terpenes (menthane), 
C 10 H 16 , methyl succinate for methyl maleate or fumerate, propionitrile 
for ethel carbylamine, and ethyl nitroethane for ethyl nitrite. 


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APPENDIX II. 


AN INVESTIGATION OF THE DICARBOXYLIC ESTERS. 


Whilst this work was passing through the press, a successful investi¬ 
gation was made of the dicarboxylic esters, a series which for a long 
time resisted treatment. They show quite a number of points of inter- 
est, especially of the influence of complexity, so that it will be useful 
to include them in an appendix at the end of the volume. 

We find that the oxalates and formates show many points of 
similarity, whilst the malonates and the succinates compare with the 
acetates. 


From the formates. 
-COOCH, 

62*7 - 4*0 as 587 

- COOC 2 H 5 
84*6 — 4*0 = 8o*6 

Dimethyl oxalate. 

Vm . (COOCH,) a 
« 2 x 587 = 117*4 
Observed 117*4 
Methyl ethyl oxalate. 
COOCH, 

Vm | 

COOC a H, 

= 58*7 + 8o*6 = 139*3 
Observed 139*4 


From the acetates. 

-COOCH, 

83*2 - 25*9 = 57*3 
-CH a . COOCH, 

83*2 - 4*0 = 79*2 

Dimethyl malonate. 

COOCH, 

V m CH-/ 

COOCH, 

- 79 ' 2 + 587 - I 37‘9 
Observed 137*9 


The Oxalates (Wiens Konigsberg Inaug. Diss., 1887). 


COOCH, 

V w . 

5nVa. 

For complexity 
+ » x 3*3 

Calc. 

toOCH, 

COOCH, 

”7*4 

”7*4 

— 

117*4 

toOC,H, 

COOC.H, 

1 

139*4 

139*4 

— 

139*4 

COOC a H 6 

cooc,h 7 

162*2 

161*8 

— 

161*8 

toOC,H 7 

COOC.H, 

215*8 

205*4 

117*4 + 4 X 22*0 

3 x 3*3 

9*9 

2i5*3 

1 

COOC 7 Hu 

316-5 

293*4 

265 

7 x 3*3 

23*1 

316-5 


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266 


LIQUID CHEMICAL COMPOUNDS. 


COOCjHj 

toOC,H„ 


341*9 315*4 

The Malonates. 


/ 


COOCH, 


CHo 


\ 


COOCH, 

COOC.H, 


137*9 


/ 

CH, 

\ 


J n 5 


/ 

CH, 

\ 


COOC,H 5 1856 

cooc,h 7 


137*9 


181*9 

137*9 + 44 *o 


COOC,H 7 235*0 225*9 

The Succinates. 


8 x 33 
26*4 


1 X 3*3 


3 x 3*3 
9*9 


341-8 


137*9 


l85*2 


235*8 


CH,—COOCH, 

llH, — COOCH, 
CH,—COOC.Hj 

1 

160*0 




CH,—COOC,H 7 

CH,—COOC,H 5 

257*2 

248*0 

160 + 4 X 22*0 

3 x 3*3 

9*9 

257*9 

im,—COOC,H, 
CH,—COOC,H 5 

2320 

226*0 

2 x 3*3 
6*6 

232*6 

I:h,—cooc,h u 

CH,—COOC 7 H 15 

333-6 

314*0 

6 x 3*3 
ig*8 

333-8 

Lh,—cooc 7 h 15 

460*6 

424*0 

11 x 3*3 
36*3 

460-3 


The rule for increase due to complexity in the case of Wien’s com¬ 
pounds is : Add 22*0 for every CH 2 added after the simple methyl com - 
pounds , and an additional 3*3 for every CH 2 added beyond 3CH 2 . One 
observation of some significance is, that the increase due to complexity 
is rectilinear. This has been found to be the case in the 

{ Acrylic esters CH, = CH—COOR 
Phenolic ethers C 6 H 8 —OR and other aromatic esters 
Dicarboxylic esters (COOR),, CH, (COOR),, C,H 4 (COOR),. 


On the other hand we find that in the case of the aliphatic ethers 
R—O—R 1 the augmentation depends upon the square of the complexity. 
These effects are probably due to the following features. In the 


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APPENDIX II. 


267 ' 


first series, the augmentation only affects the hydrocarbon (paraffinoid) 
radicals R, and since the saturated carbon chain extends only on one 
side, the augmentation depends on the complexity simply. 

H—COOCH a . CH a . CH S . CH a . CH 8 . 

In the aliphatic ethers the augmentation depends on the square of 
the complexity , because the saturated carbon chain extends on both sides 
of the oxygen atom. 

<- - > 

CH 8 . CH a . CH 3 . CH 3 —O—CH a . CH a . CH a . CH 8 . 

There are indications that this is also the case in the symmetrical 
normal paraffins. 

CH S . CH a . CH a . CH a . CH a . CH a . CH a . CH S . 

If the radicals on one side are substituted, or if the phenyl or other 
similar radical replace the saturated aliphatic radical, so rendering the 
compound non-symmetrical, the simple rule obtains. If, however, there 
be a symmetrical arrangement on both sides the rule is more complex. 
This more complicated rule suggests interaction between the two radicals . 
This might be the case if the arrangement of the atoms were as in the 
scheme. 


CH S . CH a . CH a . CH 2 

\ 

o 

/ 

CH 3 .CH a .CH 2 .CH 3 

The facts in favour of the disposition of the oxygen valencies shown 
by ^>0 are numerous. Considerable differences in the complexity of 

the two radicals generally cause a diminution however. This suggests 
important modifications in the configuration of oxygen compounds or 
rather they show that the configurations follow from a similar law to that 
which governs the tetrahedral arrangement of groups about the carbon 
atom. 


ch 8 ch 8 ch 8 ch 8 .ch 2 ch 3 —ch 2 —c = o 

Ah— ch c! = ch ch,— A 

Ah, Ah, Ah, Ah, ch,^ 

In all these cases there are augmentations in the boiling-point and 
diminutions in the volume. 

It is noticed that among Wiens 1 compounds is the di-heptyl succin¬ 
ate, which contains no fewer than 53 atoms and the very large molecular 
volume of 460 c.c. or nearly 500 c.c. This is the largest molecule with 
which we have had to deal in the course of this investigation'. 


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268 


LIQUID CHEMICAL COMPOUNDS . 


H 


\ 

( 

/ 


H 


H 


\ 

< 

/ 


H 


Dipeptyl Succinate C 9 H 4 (COOGyH^),. 

O HHHHHHH 

ijiujjj. 

1111 jj i 

H H H H H H H 
HHHHHHH 

-C—O— J— 0—1— J—J-J-J— H 

!! I II I I II 

O HHHHHHH 


Finally it should be stated that some of Wiens' numbers differ un¬ 


accountably from the expected values. 



COOC,H, 

/ 

V*. 

InVa. 

A. 

CH '\ 

COOC,H, 

COOC 4 H* 

/ 

208*2 

210*5 * 

— 2*3 

CH* 

\ 

cooc 4 h* 

CH*—COOC.H, 

280*0 

286*4 

— 6*4 

<!h,—COOC 4 H, 

278-4 

283*2 

— 4*8 


it is at present impossible to account for these differences. They 
are far larger than any probable error due to faulty experiment or even 
to impurity of liquid. Another very remarkable feature is that Weger 
gives data which are somewhat different to those which might be expected 
from Wiens' results, and yet show a regularity so far as the increase due 
to complexity is concerned. The compounds are succinates. 



V m . 

2*V a . 

For complex calc. (Wiens). 


CH 9 —COOCHj 

160*0 





<!h*—COOCH, 





(Weger) 

CH*—COOCH, 






<!h*—cooc*h 4 

185*0 

182*0 

1 x 3*3 

185-3 

182*0 

(Weger) 



A 33 


CH*—COOCjH, 




210*6 


(Ih,—COOCjHj 

210*3 

204*0 

2 x 3*3 

207*3 

(Weger) 



A 3*3 

CH*—COOC,H, 






(!h,—COOC.H, 

257*2 

248*0 

3 x 3*3 

261*2 

257*9 

(Wiens) 



A 3*3 



* This is the volume of the isomeric ethyl succinate C 9 H 4 (COOC 9 H B ) 9 accord¬ 
ing to Weger. 


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APPENDIX II 


269 


In the first three cases Wiens* results are 3*3 units smaller than those 
of Weger, but in the fourth case which was determined by Wiens, the 
latter regularity applies and Weger’s regularity shows a result 3 *3 too 
high. These facts, taken together with the anomalous results due to 
Wiens which show differences equal to 3*3 or some multiple thereof, 
leave us with the impression that these augmentations for some reason 
unknown may in part fail. The principle involved is that a liquid sub¬ 
stance, which so far as we know, is the same structurally, may possess 
two or more values, and that thus the volume of liquids may be variable 
for unknown reasons. A similar case, is when a substance assumes the 
liquid state, whereas the temperature conditions demand that it should be 
a solid. The condition is, however, an unstable one, and slight causes 
will lead to ordinary conditions. Another case is that of a liquid which 
shows a variable surface tension owing to slight amounts of impurity. 
In the light of this, we might suppose that the intermolecular forces are 
also capable of being rendered latent and inoperative for a similar 
reason. 

A comparison of the boiling-points show considerable irregularities. 
This might be expected to be the case. 

The regularity demanded by Weger’s results nearly all show an aug¬ 
mentation after the methyl compound in the case of the esters. Wiens* 
results all show an augmentation after the third carbon atom in the 
radicals. There is thus a constant difference of about 3*3 between 
Weger's results and those due to Wiens. 


The Volumes of Geometrical Isomers . 


It will now be interesting to calculate the volumes of a number of 
geometrical isomers, constructed according to the well-known malenoid 
and fumaroid types. 

CH—X X—CH 


II II 

CH—Y CH—Y 

“Adjacent.** “Opposed.** 

In order to do this, we need to know the values of c for the corre¬ 
sponding saturated compounds. The data for the dicarboxylic esters 
give us the necessary means of doing this and so of solving the problem. 
The compounds open to investigation are :— 


“ Adjacent.*’ 

Ethyl maleate. 
C 8 H ia 0 4 b.p. 225-0 
d* 1-06917 
Propyl maleate. 
b.p. 

djo 1*02899 
Methyl maleate. 
CjHgCV^b.p. 205 

dy 1-15172 


“ Opposed.** 
Ethyl fumarate. 
b.p. 206*2 
d«o 1*05200 
Propyl fumarate. 

d*o 1-02203 


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270 


LIQUID CHEMICAL COMPOUNDS. 


Methyl succinate. 

B.p. d 0 . 

d C. 

B.p. 

0*912 0*59 

c,h X() o 4 

195*2 1*1162 (<f 18 ) 

Ethyl succinate. 

c 8 h 14 o 4 

215*4 1*0596 

0*82726 0*635 

Ethyl propyl succinate. 

c,h..o 4 

231*0 1*03866 

0*81476 0*658 

Ethyl butyl succinate. 

CioH] 8 0 4 

247 1*02178 

0*78572 0*639 

Applying these values we find :— 


Methyl succinate. 


Methyl maleate. 

CH a —COOCH 8 


CH—COOCH 8 

I 

A 

II 

CH 2 —COOCH s 


CH—COOCH 8 

b.p. 195*2° V*» 160*0 

-6*5 

153*5 b.p. 205° 

Ethyl succinate. 


Ethyl maleate. 

CH a —C00C 2 H 5 


CH—COOC 2 H b 
|| 

in.— cooc,h. 


CH—COOC t H B 

b.p. 2x5® V)» 210*3 

— 7 *o 

203*3 b.p. 225° 

Propyl succinate. 


Propyl maleate. 

CH,—COOCjHj 


CH—COOC 8 H 7 
|| 

Ah,—COOC,H 7 


CH—COOC 8 H 7 

b.p. 247 0 V m 258*4 

—8*4 

250*0 b.p. 257° 


The Fumarates. 

Ethyl fumarate C 8 H 12 0 4 . 
C 2 H B OOC—CH 

II 

HC—COOC 2 H B 
b.p. 218° d % o 1*05200 

Vw 204*5 

A + 1*2 

Ethyl maleate <203*3 
Propyl fumarate ^ 10 ^ 16 ^ 4 * 

C 3 H 7 . OOC—CH 

II 


HC—COOC 8 H 7 
b.p. 250° d % 01*02203 

V*» 250*8 

A + o*8 

Propyl maleate 250*0 


It is seen that the maleic esters differ from the corresponding succinic 
esters by about the volume of H 2 = 7 *2 which represents their difference 
in composition. 

The furmaric esters are about a unit larger. 

We might expect the former to manifest the above differences. At 
any rate it shows that the succinic and no doubt the malonic and oxalic 
esters are constructed according to the adjacent types. 

COOR COOR CH 2 —COOR 

I CH, | 


COOR 1 


\ 

COOR 1 


CH„—COOR 1 


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APPENDIX II 


271 


The smallness of the differences between the volumes of members 
of the two series is doubtless owing to the small reactivity of the groups 
COOR. This is in conformity with chemical observation which shows 
that succinic anhydride may be formed from succinic derivatives. 

If we try to account for the actual volumes of the succinates and the 
maleates, etc., we obtain the following results :— 

Ethyl formate HCOOC 2 H 6 Vm 84*6 

Ethyl propionate CH 3 . CH 2 . COOC 2 H B 1277 


CH a —COOCoH s 


c 2 h 4 

84*6 - 4*0 = 8o*6 
2fcOOC 2 H B 161 *2 


43 *i 


2CH 2 43*1 


CH 2 —COOC 2 H b 

For complexity 


204*3 
+ 6*6 


'ZnVa 210*9 
Ethyl succinate Vm 210*3 

2COOC 2 H b 161*2 

CH—COOC 2 H b 

II zCH 35-9 


CH—COOC,H 6 197-1 

For complexity + 6*6 


2»V a 203*7 
Ethyl maleate V m 203*3 

The above instances of geometrical isomerism are too few in number 
upon which to build any general hypothesis, they merely serve as indi¬ 
cations of what might be expected. 


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REFERENCES. 


I Le Bas, J.C.S., Trans., 91, 112 (1907). 

9 Krafft, Ber., 15, 1687, 1711 (1882); 19, 2218 (1886). 

3 Le Bas, Phil. Mag. [6], 14, 81, 333 (1907). 

4 Baeyer, Ber., 10, 1286-7 ( i8 77 )* 

5 Le Bas, Journ. Chem. Soc. Proc., 27, 196 (1911). 

6 Biach, Zeits. Phys. Chem., 50, 43 (1905). 

7 Le Bas, Phil. Mag. [6], 16, 91, 66 (1908). 

8 Krafft, Ber., 16, 3018 (1883); 17, 1371 (1884). 

9 Krafft, Ber., 15, 1728 (1882). 

10 Schiff, Ann., 223, 247 (1884). 

II Kopp, Ann., 96, 153, 303 (1855). 

12 Le Bas, Phil. Mag. [6], 16, 91, 60 (1908). 

18 Buff, Ann. Suppl., 4, 129 (1865). 

34 Schiff, Ann., 220, 301 (1883). 

15 Lossen, Ann., 254, 42 (1889). 

16 Gartenmeister, Ann., 233, 249 (1886). 

17 Dobriner, Ann., 243, 11 (1888). 

18 Schiff, G.C.I., 13, 177 (1883). 

19 Pinette, Ann., 243, 32 (1888). 

20 Zander, Ann., 225,174 (1884). 

21 Young, Brit. Assoc. Report, Cambridge (1904). 

22 Le Bas, Phil. Mag. [6], 14, 81, 337 (1907). 

23 Naumann, Ber., 7, 173, 206 (1874). 

24 Schiff, Ber., 15, 2974 (1882). 

25 Pinette, Ann., 243, 50 (1888). 

26 Neubeck, Zeits. Phys. Ch., 1, 656 (1887). 

27 Perkin, Journ. Chem. Soc., Trans., 81, 292 (1902). 

28 (1) Kehrmann, Journ. Chem. Soc., Trans. ? 

(2) O. M. Foster, Journ. Chem. Soc., Trans., 81, 268 (1902). 

29 Schiff, Gazz. C. Ital., 13, 177 (1881). 

30 Le Bas, Phil. Mag. [6], 28, 439 (1914). 

31 F. Swartz, Journ. Chem. Soc., Abs. i., 129, 82 (1901). 

•— 32 Thorpe, Journ. Chem. Soc., Trans., 37, 201, 371 (1880). 

38 Jungffeisch, Jahresb. liber die Fortschritte der Chemie, 19, 551; 20, 36. 

34 Le Bas, Phil. Mag., 27, 988 (1914). 

35 Le Bas, Chem. News (1909). 

86 Le Bas, Phil. Mag., 27, 976 (1914). 

^. 37 Thorpe, Journ. Chem. Soc., 37, 360 (1882). 
as Weger, Ann., 221, 61 (1883). 

89 Dobriner, Ann., 243, 1 (1888). 

40 Le Bas, Phil. Mag. [6], 27, 750 (1914). 

41 Gartenmeister, Beibl., 9, 766 (1885); Ann., 233, 249 (1886). 

42 Hinrichs, Jahresb., etc., 1868, p. 80. 

43 Pinette, Ann., 243, 32 (1888). 

273 


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*74 


Liquid chemical compounds . 


44 Schiff, G.C.I., 13, 177 (1883). 

44 Zander, Ann., 224, 48 (1884); Schiff, G.C.I., 13, 177 (1883). 

48 Gartenmeister, Ann., 233, 249 (1886); Schiff, G.C.I., 13, 177 (1883). 
Els&sser, Ann., 2x8, 302 (1883). 

47 Wiens, Konigsberg, Inaug. Diss. (1887); Weger, Ann., 221, 61 (1883). 

48 Weger, Ann., 221, 61 (1883). 

44 Schiff, G.C.I., 13, 177 (1883). 

#0 Weger, Ann., 221, 61 (1883). 

41 Weger, do., do., do. 

48 Ramsay, Journ. Chem. Soc., Trans., 35, 471 (1879). 

48 Schiff, Ber., 18, 1605 (1885). 

44 Briihl, Ber., 39, 2752 (1906); 40, 4183 (1907). 


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BIBLIOGRAPHY. 


Kopp, Pogg. Ann., 47, 113 (1839); 5 *» 243 , 262 (1844); Ann., 41, 79 (1842); 96, 
153 , 303 (1855); 250 , 1 (1889). 

Constitutive Relations. 

(z) The Homologous Increment :— 

Gartenmeister, Ann., 233, 249 (1886); Pinette, Ann., 243, 32 (1888); Dobriner, 
Ann., 243, n (1888); Elsasser, 218, 337(1883); Zander, Ann., 225, 74 
(1884); Lossen, 254, 42 (1889). 

(2) Isomerides: — 

Horstmann, Beziehungen zwischen der Raumerfullung und chemischer 
Zusammensetzung; Graham-Otto Lehrbuch der Chemie, vol. i., 3 (1898). 
Krafft, Ber., 15, 1711 (1882); 17, 1371 (1884). 

Brown, Proc. Roy. Soc., 26, 247 (1878); Dobriner, Ann., 243, 30 (1888): 

Fettler, Zeit. Phys. Chem., 4, 66 (1889). 

Gartenmeister, Ann., 233, 249 (1886); Neubeck, Zeit. Phys. Chem., I, 649 
(1887); Pinette, Ann., 243 (1888); Ramsay, Trans. Chem. Soc., 35, 463 
(1879); Schiff, Ann., 220, 71, 278 (1883); Ber., 14, 2761 (1881); Stadel, 
Ber., IS 2559 (1889). 

Thorpe, Trans. Chem. Soc., 37, 141, 327 (1880); Zander, Ann., 224, 74 
(1884); Schroder, Ber., 13, 1560 (1880). 

Stereoisomerides :— 

Walden, Ber., 29, 1699 (1896); Liebisch, Ann., 286, 140 (1895); Traube, 
Ann., 240, 43 (1886). 

Unsaturation :— 

Buff, Ann. Suppl., 4, 129 (1865); Schiff, Ann., 220, 301 (1883); Lossen, 
Ann., 254, 42 (1889); 214, 81 (1883); Krafft, Ber., 17, 1371 (1884); 
Zander, Ann., 214, 138 (1882); Horstmann, Graham-Otto Lehrbuch 
der Chemie, vol. i., 3, p. 422 (1880); Schiff, Ann., 220, 71 (1883); 
Zander, Ann., 114, 138 (i860); Krafft, Ber., 17, 1371 (1884). 

Ring formation :— 

Willstatter, Ber., 41, 1480 (1908). 

The author’s work deals with all of the above features. 

The chief papers are:— 

Trans. Chem. Soc., 91,112 (1907); Phil. Mag. [6], 14,324 (1907); 16, 60 (1908); 
Chem. News, 98, 85 (1908); 99, 206 (1909); Phil. Mag., 27, pp. 344, 741, 976; 28, 
P- 439 (1914)- 

The Influence of Constitution on the Molecular Volumes of Organic Com¬ 
pounds at the Boiling-point. Brit. Assoc. Meeting, Section B, Portsmouth 
(1911). 

The Influence of the Alternating Factor in certain series on the Molecular 
Volumes at the Melting-point. Proc. Chem. Soc., 27, 196 (1911). 

A Formula by means of which the Molecular Volume at the Boiling-point may 
be Calculated. Proc. Chem. Soc., 30, 86 (1914). 

Molecular Volume Theories and their relations to current conceptions of 
Liquid Structure Science Progress, 32, 663 (1914). 

275 


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